Unit 5 Atomic structure (P.2)

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Unit 5 Atomic structure 原子結構

Unit 5 Atomic structure (P.2)

5.1 What is an element made of? (P.2)

All elements are made of atoms. The atoms of different elements are different.

第 5節原子結構

5.1 元素是由甚麼東西組成的？

所有元素都由原子組成。不同的元素的原子是不同的。

cut切割

cut切割

copper銅

cut切割

cut切割

cut切割

etc.

1 piece of copper1片銅

2 pieces of copper2片銅

4 pieces of copper4片銅

etc.

Fig. 5.1 Cutting a piece of copper into halves 把銅片不斷切割成半

5.2 Symbols for elements (P.2)

Chemists use symbols to represent elements. The symbols for many elements are the fi rst letters of their names. When there are several elements beginning with the same letter, a second letter is used.

Some symbols are taken from the Latin names of the elements.

5.2 元素的符號

化學家使用符號來代表元素。這些符號多是元素英文名稱的首個字母，若某些元素英文名稱的首個字母相同，就會加上另一個字母。

有些元素的符號源自該元素的拉丁文名稱。

Table 5.1 Symbols for some common elements一些常見元素的符號

Element元素

Symbol (first letter of the name)

符號（來自英文名稱的首個字母）

Element元素

Symbol (two letters from the name)符號（來自英文名稱的兩個字母）

Element元素

Symbol (taken from the Latin name)

符號（源自拉丁文名稱）

Carbon 碳 C Aluminium 鋁 Al Copper 銅 Cu

Hydrogen 氫 H Argon 氬 Ar Iron 鐵 Fe

Nitrogen 氮 N Calcium 鈣 Ca Potassium 鉀 K

Oxygen 氧 O Chlorine 氯 Cl Sodium 鈉 Na

Sulphur 硫 S Magnesium 鎂 Mg

Silicon 硅 Si

Topic 2 Microscopic World I 微觀世界 I

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Complete the following table.完成下表。

5.3 States of elements (P.3)

Elements exist in different states at room temperature and pressure. For example, silver and sulphur are solids, bromine and mercury are liquids, while chlorine is a gas.

5.3 元素的狀態

在常温常壓下，元素以不同的狀態存在。例如銀和硫是固體，溴和汞是液體，氯則是氣體。

(a) Sulphur — a solid element 硫 — 固體

(c) Chlorine — a gaseous element 氯 — 氣體

Fig. 5.2 The states of some common elements at room temperature and pressure 一些常見的元素在常温常壓下的狀態

(b) Bromine — a liquid element 溴 — 液體

Element元素

Symbol符號

State at room temperature and pressure在常温常壓下的狀態

Aluminium 鋁

Calcium 鈣

Hydrogen 氫

Sodium 鈉

Cl

K

O

S

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5.4 How to classify elements? (P.5)

Metals and non-metals

We can classify elements in many different ways. We can use the properties of an element to classify it as a metal or a non-metal.

Most of the elements are metals.

5.4 如何把元素分類？

金屬和非金屬

我們可以用很多不同的方法把元素分類。我們可根據元素的性質，將之分類為金屬或非金屬。

大部分的元素都是金屬。

Table 5.2 Comparing the general properties of metals and non-metals金屬和非金屬的一般性質的差異

Property性質

Metals金屬

Non-metals非金屬


solids (except mercury)固體（汞除外）

a few solids (e.g. carbon, sulphur); many gases (e.g. nitrogen, oxygen) but only one liquid (bromine)少部分是固體（例如碳、硫），大部分是氣體（例如氮、氧），只有一種是液體（溴）

Melting and boiling points熔點和沸點

usually high通常很高

often low一般很低

Appearance 外觀

shiny表面有光澤

usually dull if they are solids固體的表面一般是晦暗無光

Electrical conductivity導電性

good conductors良好

non-conductors (except graphite)非導電體（石墨除外）

Heat conductivity導熱性

good conductors良好

poor conductors差劣

Effect of bending and hammering彎曲和錘擊的結果

can be bent or hammered into shape可被彎曲或錘擊成各種形狀

brittle if they are solids固體易碎

Metalloids

Silicon has some properties similar to those of metals and some properties similar to those of non-metals. Silicon belongs to a group of elements called metalloids.

類金屬

硅既具有金屬的性質，也具有非金屬的性質。硅屬於一組稱為類金屬的元素。


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Table 5.3 Some properties of silicon硅的一些性質

Property 性質

Silicon (a metalloid)硅（一種類金屬）


solid固體

Melting and boiling points熔點和沸點

high高

Appearance外觀

grey and shiny crystals, or brown powder呈灰色有光澤的結晶體或呈褐色的粉末


crystalline form conducts electricity, brown powder form does not conduct electricity結晶體可導電；褐色粉末不導電

Effect of bending and hammering彎曲和錘擊的結果

brittle易碎

1 Study the following list of elements: 細閱下列元素：

carbon, mercury, oxygen, silicon, sodium. 碳、汞、氧、硅和鈉。

a) Which of the above elements is / are metal(s)? 以上哪種 / 些元素是金屬？

b) Which of the above elements is a metalloid? 以上哪一種元素是類金屬？

c) Which of the above elements is / are non-metal(s)? 以上哪種 / 些元素是非金屬？

d) Which non-metal is a solid at room temperature and pressure? 以上哪一種元素是在常温常壓下以固體形式存在的非金屬？

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5.5 Basic structure of an atom (P.8)

Atoms consist of a nucleus and a cloud of electrons that move around the nucleus. The nucleus itself contains two types of particles: protons and neutrons. Protons, neutrons and electrons are called subatomic particles.

5.5 原子的基本結構

原子由原子核和一團圍繞着原子核移動的電子組成。原子核內有兩種粒子：質子和中子。質子、中子和電子稱為次原子粒子。

2 Study the following descriptions of three elements. Classify each as a metal, non-metal or metalloid. Explain your choice in each case.

細閱下列有關三種元素的描述。試把它們分類為金屬、非金屬或類金屬，並加以解釋。

Element元素

Description描述

Xa yellow solid that melts at 119 °C; both the solid and liquid forms do not conduct electricity熔點為 119 °C的黃色固體，在固態和液態時都不導電

Ya shiny solid which can be bent or hammered into shape easily表面有光澤的固體，可輕易被彎曲或錘擊成各種形狀

Za shiny brittle solid which can conduct electricity易碎，表面有光澤及能導電的固體

Fig. 5.3 A model for the structure of an atom 原子的結構

key:索引：

cloud of electrons一團移動的電子

proton質子

neutron中子

nucleus原子核

proton質子neutron中子

5.6 Atomic number (P.9)

The atomic number of an element is the number of protons in an atom of that element.

An atom has equal numbers of protons and electrons.

5.6 原子序

一種元素的原子序是該元素原子內的質子數目。

原子的質子數目和電子數目相同。


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Table 5.4 Number of subatomic particles in atoms of the 20 simplest elements20種最簡單的元素的原子內次原子粒子的數目

Atom原子

Symbol符號

Number of protons (atomic number)質子數目（原子序）

Number of neutrons中子數目

Number of electrons電子數目

Hydrogen 氫 H 1 0 1

Helium 氦 He 2 2 2

Lithium 鋰 Li 3 4 3

Beryllium 鈹 Be 4 5 4

Boron 硼 B 5 6 5

Carbon 碳 C 6 6 6

Nitrogen 氮 N 7 7 7

Oxygen 氧 O 8 8 8

Fluorine 氟 F 9 10 9

Neon 氖 Ne 10 10 10

Sodium 鈉 Na 11 12 11

Magnesium 鎂 Mg 12 12 12

Aluminium鋁 Al 13 14 13

Silicon 硅 Si 14 14 14

Phosphorus 磷 P 15 16 15

Sulphur 硫 S 16 16 16

Chlorine 氯 Cl 17 18 17

Argon 氬 Ar 18 22 18

Potassium 鉀 K 19 20 19

Calcium 鈣 Ca 20 20 20

Each element has a unique atomic number, which is used to identify the element.

每種元素都具有獨一無二的原子序，可以用來辨別該元素。

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5.7 Mass number (P.11)

The mass number of an atom is the sum of the numbers of protons and neutrons in the atom.

5.7 質量數

原子的質量數相等於其原子內質子數目與中子數目的總和。

1 How many protons, neutrons and electrons are there in each of the following atoms? 下列各種元素的原子內分別有多少個質子、中子和電子？

a) 73Li b) 2

137Al c) 4

200Ca

2 Complete the following table. 完成下表。

Atom原子

Atomic number原子序

Mass number質量數

Number of次原子粒子數目

protons質子

neutrons中子

electrons電子

Fluorine氟

9 10

Boron硼

11 5

Phosphorus磷

15 31

5.8 Isotopes (P.12) 5.8 同位素

Isotopes are different atoms of an element which have the same number of protons but a different number of neutrons.

同位素是同一種元素的不同原子，它們具有相同數目的質子，但中子的數目卻不同。

Although the isotopes of an element have different masses and physical properties, they have the same chemical properties.

Most elements have more than one isotope.

雖然同一種元素的同位素各有不同的質量和物理性質，但它們具有相同的化學性質。

大部分的元素都擁有多於一種同位素。


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Table 5.5 Isotopes of some elements一些元素的同位素

Element元素

Name of isotope同位素的名稱

Symbol符號

Mass number質量數

Number of次原子粒子數目

protons質子

neutrons中子

electrons電子

Hydrogen氫

Protium氕（音：撇）Deuterium氘（音：刀）

Tritium氚（音：川）

11H

21H

31H

1

2

3

1

1

1

0

1

2

1

1

1

Carbon碳

Carbon-12碳 -12

Carbon-13碳 -13

Carbon-14碳 -14

162C

163C

164C

12

13

14

6

6

6

6

7

8

6

6

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5.9 Relative masses of atoms and the carbon-12 scale (P.13)

Relative isotopic mass

Atoms are so light that it is difficult to weigh them. Ordinary units are unsuitable for measuring them. Scientists chose the carbon-12 (1

62C) atom to be the standard atom.

One carbon-12 atom contains six protons and six neutrons and has a mass number of 12. Chemists have defi ned the carbon-12 atom as having a mass of exactly 12.00. By comparing the mass of an isotope of an element with this standard, we can obtain the relative isotopic mass of that particular isotope of the element.

5.9 原子的相對質量和碳 - 12基準

相對同位素質量

原子非常輕，一般的單位並不適宜用來稱量它們。化學家選擇碳 -12 原子（ 1

62C）作為基準。一個碳 -12 原

子具有六個質子和六個中子，質量數是 12，化學家把碳 -12的質量定為 12.00。將元素的同位素的質量與這個基準比較，我們便可得出元素的該同位素的相對同位素質量。

The relative isotopic mass of a particular isotope of an element is the relative mass of one atom of that isotope on the 12C = 12.00 scale.

一種元素的某一個同位素的相對同位素質量，是按 12C = 12.00的基準計算該同位素單一個原子的相對質量。

The relative isotopic mass of an isotope is roughly equal to its mass number.

一個同位素的相對同位素質量大約等於它的質量數。

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Relative atomic mass

Most elements have more than one isotope. The different isotopes of each element have different relative isotopic masses. However, for the element as a whole, there is only one relative atomic mass. We must consider the relative isotopic mass and relative abundance of each isotope of an element in nature when calculating the relative atomic mass of that element.

相對原子質量

大部分的元素都擁有多於一種同位素。每種元素的同位素都具有不同的相對同位素質量。然而，一種元素只有一個相對原子質量。計算一種元素的相對原子質量時，必須考慮該元素每個同位素的相對同位素質量和其相對豐度。

The relative atomic mass of an element is the weighted average relative isotopic mass of all the naturally occurring isotopes of that element on the 12C = 12.00 scale.

一種元素的相對原子質量是按12C = 12.00的基準，該元素所有在自然界存在的同位素的相對同位素質量的加權平均數。

Table 5.6 Relative atomic masses of some common elements一些常見元素的相對原子質量

Element元素

Symbol符號

Relative atomic mass相對原子質量

Element元素

Symbol符號


Aluminium鋁

Al 27.0Magnesium

鎂Mg 24.3

Calcium鈣

Ca 40.1Oxygen氧

O 16.0

Chlorine氯

Cl 35.5Potassium鉀

K 39.1

Copper銅

Cu 63.5Silver銀

Ag 107.9

Hydrogen氫

H 1.0Sodium鈉

Na 23.0

Iron鐵

Fe 55.8Sulphur硫

S 32.1


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1 Calculate the relative atomic mass of magnesium. 根據下表資料，計算鎂的相對原子質量。

Isotope同位素

24Mg 25Mg 26Mg

Relative abundance (%)相對豐度（%）

78.6 10.1 11.3

2 Boron consists of two isotopes: 150B and 1

51B. The relative atomic mass of boron is 10.8. Calculate the relative

abundance of the isotopes. 硼有兩種同位素，分別是 1

50B和 1

51B。硼的相對原子質量是 10.8。計算這兩種同位素的相對豐度。

3 An element X has a relative atomic mass of 87.6, yet no atom of X has this relative mass. Explain. 元素 X的相對原子質量是 87.6，可是，沒有任何 X的原子的相對質量是這個數值。解釋這現象。

5.10 The arrangement of electrons in atoms (P.16)

Electronic arrangement

Electrons move around the nucleus in circular orbits called shells.

5.10 原子內的電子排佈

電子排佈

電子是在稱為電子層的圓形軌道上繞着原子核運行的。

Fig. 5.4 Electrons move around the nucleus in shells 電子在電子層上繞着原子核運行

n = 2nucleus原子核

electrons move around the nucleus in shells電子在電子層上繞着原子核作高速運行

n = 1

n = 3

Each shell can only hold a certain number of electrons. The 1st shell can hold a maximum of 2 electrons. The 2nd shell can hold a maximum of 8 electrons. The 3rd shell can hold a maximum of 18 electrons.

每層電子層均只能容納一定數目的電子。第一層最多可容納 2個電子。第二層最多可容納 8個電子。第三層最多可容納 18個電子。

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Fig. 5.5 The maximum number of electrons the first four shells can hold 首四層電子層最多可容納的電子數目

The way in which electrons are arranged in an atom is called its electronic arrangement.

We can represent the electronic arrangement of an atom by an electron diagram.

A sodium atom has 11 electrons. The fi rst 10 electrons fill up the first and second shells while the last electron goes into the third shell. A sodium atom thus has an electronic arrangement of 2,8,1.

電子在各電子層上的排列方式稱為電子排佈。

我們可以用電子圖來表示原子內的電子排佈。

鈉原子有 11個電子，首 10個電子分別填入第一和第二層電子層，餘下的一個則填入第三層，所以鈉原子的電子排佈是 2,8,1。

nucleus原子核

1st shell can hold a maximum of 2 electrons第一層最多可容納 2 個電子 [2(1)2= 2]

2nd shell can hold a maximum of 8 electrons第二層最多可容納 8 個電子 [2(2)2 = 8]

3rd shell can hold a maximum of 18 electrons第三層最多可容納 18 個電子 [2(3)2 = 18]

4th shell can hold a maximum of 32 electrons第四層最多可容納 32 個電子 [2(4)2 = 32]

1 Draw electron diagrams for atoms of the following elements: 繪出下列元素的原子的電子圖。

a) carbon b) nitrogen c) magnesium 碳氮鎂

Fig. 5.6 Electron diagram of sodium atom 鈉原子的電子圖

Na

sodium atom鈉原子


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2 Work out the electronic arrangements for atoms of three elements (A to C) from the descriptions given below: 根據下表的資料，寫出 A至 C三種元素的原子的電子排佈。

Element元素

Description資料

Electronic arrangement原子的電子排佈

AIts atomic number is 8.它的原子序為 8。

B

Its atom has 1 completely filled shell and 7 electrons in the second shell.它的原子有一層已被填滿的電子層，第二層電子層則有 7個電子。

CIts atom has 20 electrons.它的原子有 20個電子。

3 An atom of element X has three shells. The electron diagram of its atom is shown below: 元素 X的原子有三層電子層，其原子的電子圖如下：

X

O（只顯示最外層的電子。）

X? ExX的原子序是多少 ?解釋你的答案。

X指出 X是哪一種元素。

5.11 Electrons and orbitals (P.20)

Suppose we could photograph the electron in a hydrogen atom at any given moment. The electron is moving at a high speed. The electron would occupy different positions if we took photographs at different moments. If we superimposed millions of such photographs, the resulting picture would resemble a cloud composed of a great number of dots.

Thus, in the hydrogen atom, we can imagine the electron as an electron cloud. In theory, there is no sharp boundary to the electron cloud. But we can draw a sphere enclosing about 95% of the cloud. Within the region enclosed by the sphere, there is 95% chance of fi nding the electron. The region in which there is this high probability of fi nding the electron is called an orbital.

5.11 電子與軌態

假設我們能夠在任何一刻為氫原子的電子拍攝照片。電子以高速運行，如果我們在不同時間拍照，電子會佔據不同的位置。如果我們將數以百萬計這樣的照片重疊，得出的圖像就有如一片由無數小點結集而成的雲。

因此，我們可以把氫原子的電子想像成電子雲。理論上，電子雲並無清晰的邊界。但是我們可以畫一個圓球體，包圍 95%的電子雲。在球體包圍的區域，有 95%的機會找到電子。這個有這樣大機會找到電子的區域稱為軌態。

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How ideas of the atom developed All chemistry depends on one big idea: that everything is made of atoms. But how did chemists find out about atoms?

The atomic theory

In 1807, John Dalton put forward an atomic theory to explain the structure of matter and certain aspects of chemical reactions. He suggested that all matter was made of tiny particles, which he called atoms.

Discovery of electrons and protons

I n 1897, J . J . T h o m s o n p a s s e d h i g h voltage electricity through a gas in a tube at low pressure. He found that a stream of rays, called cathode rays, moved from the negative electrode to the positive electrode. Besides, cathode rays were also deflected strongly towards the positive plate (Fig. 5.9).

原子學說的由來現今所有的化學知識都建基於一個重要的理論 — 就是所有東西都由原子組成的。可是，化學家是怎樣發現原子的呢？

原子學說

1807年，道爾頓（ John Dalton）提出原子學說，以解釋物質的結構及某些化學反應的特性。他認為，所有物質都由十分微小的粒子組成的。他稱這些粒子為原子。

電子和質子的發現

1897年，湯姆生（ J.J. Thomson）將高壓電流通過接近真空的玻璃管。他發現一束名為陰極射線的光束由負極射向正極。此外，也發現陰極射線大幅向正極電板偏移（圖 5.9）。

Fig. 5.7 John Dalton 道爾頓

Fig. 5.9 Cathode rays are deflected towards the positive plate 陰極射線向正極電板偏移

Fig. 5.8 J.J. Thomson 湯姆生

–

+

+

deflected towards the+ plate 向正極電板偏移

high voltage高電壓

to vacuum pump往真空泵

– cathode rays陰極射線

Thomson suggested that the rays were composed of particles carrying negative charges. He called them electrons.

Later Thomson discovered positive particles. He named them protons.

湯姆生認為，這些光束由帶負電荷的粒子組成，他稱這些粒子為電子。

稍後，湯姆生發現帶正電荷的粒子，他稱這些粒子為質子。


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Fig. 5.10 E. Rutherford 盧瑟福

gold atoms金原子

beam ofalpha particles

α 粒子束

nucleus原子核

Fig. 5.11 Bombardment of gold foil with alpha particles 用 α 粒子撞擊金箔

The nucleus — Rutherford’s scattering experiment

In 1911, E. Rutherford carried out a number of crucial experiments.

Thin sheets of metal foil were bombarded with positively charged particles called alpha particles. Most of the alpha particles went straight through the metal foils. Some were deflected. A few of the alpha particles bounced straight back.

原子核 — 盧瑟福散射實驗

在 1911年，盧瑟福（E. Rutherford）進行了數個十分重要的實驗。

他以一些帶正電荷的α粒子射向一片金箔。結果顯示大部分粒子都直穿過金箔，有些稍有偏移，有極少數的α粒子則被反彈回去。

Rutherford concluded that most of the atom was empty space with a small, positively charged nucleus at its centre.

In 1932, J. Chadwick discovered uncharged particles, which he called neutrons. The proposals of Rutherford and Chadwick led to a model of the atom which was composed of protons, neutrons and electrons. Protons and neutrons were packed closely together in the nucleus. Electrons moved around the nucleus at a considerable distance.

Questions

1 Dalton thought that atoms were solid balls.

a) Which piece of evidence disproved Dalton’s idea?

b) How did this evidence prove that atoms are not solid balls?

2 Why were neutrons more difficult to discover than electrons and protons?

盧瑟福指出，原子中大部分都是空間，細小、帶正電荷的原子核則位於原子的中央。

在 1 9 3 2 年，查特威克（ J. Chadwick）發現一種不帶電荷的粒子，他稱這種粒子為中子。將盧瑟福與查特威克的理論結合，就得到以下的原子模型 — 原子由質子、中子和電子組成，質子和中子緊密地擠在原子核中，電子則與原子核保持一定距離，並圍繞原子核運行。

問題

1 道爾頓認為原子是實心球體。

a) 有甚麼證據推翻道爾頓的構想？

b) 這證據怎樣證明原子並非實心球體？

2 與電子和質子相比，為甚麼中子較難被發現？

15


類金屬 m

原子核 n

電子 e

質子 p

中子 n

次原子粒子 s p

原子序 a n

質量數 m n

同位素 i

相對同位素質量 r i m

相對原子質量 r a m

相對豐度 r a

電子層 s

軌道 o

電子排佈 e a

電子圖 e d

軌態 o


16

1 All elements are made of .

2 Chemists use to represent elements.

3 At room temperature and pressure, elements exist in different states ( ,

or ).

4 Elements can be classified into three main groups — , and

.

5 An atom consists of three types of subatomic particles: , and

.

The contains protons and neutrons. move around the

nucleus in shells.

6 Atomic number of an element

= number of in an atom of that element

= number of in a atom of that element

7 = number of protons + number of neutrons

symbol of an atom

17


8 are different atoms of an element which have the same number of protons but

a different number of neutrons.

9 The of a particular isotope of an element is the relative

mass of one atom of that isotope on the 12C = 12.00 scale.

10 The of an element is the weighted average relative isotopic

mass of all the naturally occurring isotopes of that element on the 12C = 12.00 scale.

11 The way in which electrons are arranged in an atom is called its

.

nucleus

1st shell can hold a maximum of _____ electrons

2nd shell can hold a maximum of _____ electrons

3rd shell can hold a maximum of _____ electrons

4th shell can hold a maximum of _____ electrons

12 An is the region in which there is a high probability of fi nding an electron.


18

Unit 6 The periodic table (P.31)

6.2 The periodic table (P.31)

Chemists group elements with similar properties together. This gives rise to the periodic table. In the periodic table, all the elements are arranged in order of increasing atomic number.

第 6節週期表

6.2 週期表

化學家把具有相似性質的元素歸入不同組別，得出了週期表。在週期表裏，所有的元素都按原子序由小至大順序排列。

Period 2第二週期

Period 3第三週期

Period 4第四週期

Period 5第五週期

Period 6第六週期

Period 7第七週期

Period 1第一週期

atomic number原子序

GroupI

第 I族

GroupII

第 II族

Li Be

Na Mg

K Ca

GroupIII

第 III族

GroupIV

第 IV族

GroupV

第 V族

GroupVI

第 VI族

GroupVII

第 VII族

Group0

第 0族

Ga Ge As Se Br Kr

Al Si P S Cl Ar

B C N O F Ne

He

transition metals過渡金屬

Sc Ti V Cr Mn Fe Co Ni Cu Zn

H

A vertical column is called a group縱行稱為族A horizontal row is called a period橫排稱為週期

name of element元素名稱

symbol元素符號

Fig. 6.1 A simplified periodic table showing the first 36 elements 展示首36種元素的簡化週期表

Groups — the vertical columns in the periodic table

The vertical columns in the periodic table are called groups. Groups are numbered from I to VII, followed by Group 0.

族 — 週期表的縱行

週期表中的縱行稱為族。從左至右順序為第 I族至第 VII族，接着是第0族。

Table 6.1 Electronic arrangements of atoms of some elements in some groups一些同族元素的原子的電子排佈

Group I 第 I族 Group II 第 II族 Group VII 第 VII族 Group 0 第 0族

He (2)

Li (2,1) Be (2,2) F (2,7) Ne (2,8)

Na (2,8,1) Mg (2,8,2) Cl (2,8,7) Ar (2,8,8)

K (2,8,8,1) Ca (2,8,8,2) Br (2,8,18,7) Kr (2,8,18,8)

19

Unit 6 The periodic table 週期表

The group number of an element is equal to the number of outermost shell electrons in its atom. For example, every member of Group I has 1 outermost shell electron in its atom.

Atoms with the same number of outermost shell electrons react in a similar way. Elements in the same group have the same number of outermost shell electrons in their atoms, therefore they have similar chemical properties.

每種元素所屬的族數，與其原子最外層電子的數目相等。例如，第 I族元素的原子都具有 1個最外層電子。

具有相同數目的最外層電子的原子會起相類似的反應。同族元素的原子具有相同數目的最外層電子，所以它們具有相似的化學性質。

The chemical properties of an element depend on the number of outermost shell electrons in its atom.

元素的化學性質與其原子具有的最外層電子的數目有關。

Periods — the horizontal rows in the periodic table

The horizontal rows in the periodic table are called periods.

週期 — 週期表的橫排

週期表中的橫排稱為週期。

Table 6.2 Electronic arrangements of atoms of elements in periods 2 and 3第二和第三週期各元素的原子的電子排佈


Li Be B C N O F Ne

Electronic arrangement of atom原子的電子排佈

2,1 2,2 2,3 2,4 2,5 2,6 2,7 2,8


Na Mg Al Si P S Cl Ar


2,8,1 2,8,2 2,8,3 2,8,4 2,8,5 2,8,6 2,8,7 2,8,8

Atoms of elements in the same period have the same number of occupied electron shells. The atom of each element in Period 1 has one occupied electron shell.

同一週期的元素，它們的原子內被電子佔用的電子層的數目相同。第一週期內的元素的原子有一層被電子佔用的電子層。


20

Historical development of the periodic table

Tasks

You are going to search and present information on the historical development of the periodic table.

1 Your teacher will divide the class into groups. Each group should give a 4-minute presentation. Support your presentation with various aids, such as timelines, diagrams, etc.

2 Write a short report of not more than 300 words to summarize your findings.

Hints for the search

1 Which chemist arranged elements into groups he called ‘triads’? Why did he do that?

2 What is the ‘Law of octaves’? Which chemist discovered the ‘Law of octaves’?

3 What were the major findings of the Russian chemist Mendeléev?

Reference websites

1 Website of the Chemistry Department of the Michigan Technological University

http://chemistry.mtu.edu/~pcharles/SCIHISTORY/HomePage.html

Click on ‘Periodic Table’ to display the relevant articles.

2 An online encyclopedia

http://www.encyclopedia.com/html/section/periodlw_pioneeringperiodicarrangementsoftheelements.asp

3 Website of the Woodrow Wilson National Fellowship Foundation (an organization that seeks to sponsor academic excellence)

http://www.woodrow.org/teachers/ci/1992/Mendeleev.html

4 Website of Chemsoc, a website providing interesting features and useful services for the chemistry community

http://www.chemsoc.org/viselements/pages/history_ii.html

週期表的發展歷史

任務

你要搜集及匯報有關週期表的發展歷史的資料。

1 教師會將全班分為若干組。每組需要搜集有關週期表發展歷史的資料，然後進行為時四分鐘的匯報，建議利用圖片、年表等作輔助。

2 撰寫一篇不多於 300字的報告，總結搜集所得的資料。

搜尋提示

1 哪位化學家將元素分成「三元組」？為甚麼他會這樣做？

2 甚麼是「八倍律」？哪位化學家發現此定律？

3 俄羅斯化學家門德列夫有甚麼重大發現？

參考網址

1 化學系之網頁

點按「Periodic Table」以顯示有關文章。

2 一本網上百科全書

3 一個推動卓越學術的組織的網頁

4 Chemsoc之網頁，這是個給化學群體提供趣味特寫及有用服務的網頁

21


6.3 Patterns across the periodic table (P.36)

Across a period, the elements change from metals through metalloids to non-metals.

Notice that the reactivity of the elements also changes across a period. Apart from the noble gases, the most reactive elements are near the edges of the periodic table and the least reactive ones are in the centre.

6.3 橫越一週期時元素性質的變化

橫越一週期時，元素由金屬變為類金屬，再變為非金屬。

橫越一週期時，元素的活潑性也出現變化。除了貴氣體之外，左右兩邊的元素最活潑，中央部分的元素則最不活潑。

Table 6.3 Some properties of the elements in Period 3第三週期中的元素的一些性質

Element元素

Sodium鈉

Magnesium鎂

Aluminium鋁

Silicon硅

Phosphorus磷

Sulphur硫

Chlorine氯

Argon氬


solid固體

gas氣體

Melting point (°C)熔點（°C）

98 650 660 1 410 44 113 –101 –189

Boiling point (°C)沸點（°C）

890 1 120 2 450 2 680 280 445 –34 –186


good良好

moderate一般

poor極差

Type of element元素類別

metals金屬

metalloid類金屬

non-metals非金屬

Reactivity活潑性

reactive非常活潑

moderately reactive頗活潑

very unreactive非常不活潑

moderately reactive頗活潑

very reactive非常活潑

extremely unreactive極不活潑

Fig. 6.2 Different blocks of elements in the periodic table 週期表中不同類別的元素的位置




Period 5第五週期

Period 6第六週期

Period 7第七週期


GroupI

第 I族

GroupII

第 II族

Li Be

Na Mg

K Ca

GroupIII

第 III族

GroupIV

第 IV族

GroupV

第 V族

GroupVI

第 VI族

GroupVII

第 VII族

Group0

第 0族

Ga Ge As Se Br Kr

Al Si P S Cl Ar

B C N O F Ne

He

transition metals過渡金屬

Sc Ti V Cr Mn Fe Co Ni Cu Zn

H

key: metal metalloid non-metal索引：金屬類金屬非金屬


22

1 An atom of element X has the following structure: 元素 X的原子結構如下：

X

a) To which period and group of the periodic table does element X belong? 元素 X屬於週期表中的哪一週期和哪一族？

b) What is the atomic number of element X? 元素 X的原子序是多少？

c) Refer to a complete periodic table, name element X. 從一個完整的週期表，找出 X是哪一種元素。

d) Name another element you would expect to have similar chemical properties. 舉出一種化學性質與 X相似的元素。

2 The following is a part of the periodic table. (The letters are NOT the symbols of the elements.) 以下是週期表的其中一部分，元素以英文字母表示。（這些英文字母並非元素符號。）




GroupI

第 I族

GroupII

第 II族

GroupIII

第 III族

GroupIV

第 IV族

GroupV

第 V族

GroupVI

第 VI族

GroupVII

第 VII族

Group0

第 0族

a

b

c

d e f g h i j

a) Across a period, the elements show a gradual change in some physical properties. Suggest ONE such property.

橫越一週期時，元素的物理性質依次遞變。舉出一項這樣的性質。

b) How many outermost shell electrons are there in an atom of g? 在元素 g的原子內，有多少個最外層電子？

c) How many occupied electron shells are there in an atom of h? 在元素 h的原子內，有多少被電子佔用的電子層？

d) Classify each element into a metal, metalloid or non-metal. 將表中的元素分類為金屬、類金屬或非金屬。

23


6.4 Group I elements — alkali metals (P.38)

The six elements in Group I are lithium, sodium, potassium, rubidium, caesium and francium. These elements react with water to form alkalis. Hence they are called the alkali metals.

The melting point and boiling point of the elements decrease as we move down the group.

6.4 第 I族元素 — 鹼金屬

第 I族的六種元素分別是鋰、鈉、鉀、銣、銫和鈁。它們都會與水反應生成鹼，因此，它們稱為鹼金屬。

這些元素的熔點和沸點由上至下依次遞減。

Table 6.4 Some physical properties of Group I elements第 I族元素的一些物理性質

Element元素

State at roomtemperature and pressure在常温常壓下的狀態



Density (g cm–3)密度（g cm–3）

Lithium鋰

solid固體

180 1 330 0.53

Sodium鈉

98 890 0.97

Potassium 鉀

64 760 0.86

Rubidium銣

39 686 1.53

Caesium銫

29 669 1.88

Francium鈁

27 677 —

Similarities of Group I elements

1 They all have relatively low melting and boiling points when compared with other metals.

2 They are all soft and can be cut with a knife.

3 They all have low densities — lithium, sodium and potassium fl oat on water.

4 They are all reactive metals and must be stored in paraffi n oil to prevent them from reacting with the air.

5 They all react vigorously with water to give hydrogen gas and an alkaline solution.

6 They all react with non-metals to form compounds called salts.

第 I族元素相似的性質

1 與其他金屬相比，第 I族元素的熔點和沸點都較低。

2 它們都是軟金屬，可用刀切割。

3 它們具有低密度 — 鋰、鈉和鉀都可浮於水面。

4 它們都是活潑的金屬，必須貯存於石蠟油中，防止它們與空氣反應。

5 它們會與水產生劇烈的化學反應，釋出氫氣和生成鹼性溶液。

6 它們會與非金屬反應，生成稱為鹽的化合物。


24

第 I族元素活潑性的差異

同族的元素有相似的化學性質。可是，它們的活潑性會由上至下依次遞變。

第 I族的元素都非常活潑，元素的活潑性由上至下依次遞增。

6.5 第 II族元素 — 鹼土金屬

第 II族的六種元素分別是鈹、鎂、鈣、鍶、鋇和鐳。這些元素都可在泥土中找到，並會與水反應生成鹼，因此，它們稱為鹼土金屬。

Differences in reactivity of Group I elements

Elements in the same group of the periodic table have similar chemical properties. However, there is a gradual change in the reactivity of the elements as we move down a group.

Group I elements are all very reactive. The reactivity of these elements increases as we move down the group.

6.5 Group II elements — alkaline earth metals (P.41)

The six elements in Group II are beryllium, magnesium, calcium, strontium, barium and radium. These elements are found on the Earth and react with water to form alkalis. Hence they are called the alkaline earth metals.

Table 6.5 Some physical properties of the Group II elements第 II族元素的一些物理性質

Element元素





Beryllium鈹

solid固體

1 280 2 480 1.85

Magnesium鎂

650 1 120 1.74

Calcium鈣

838 1 440 1.55

Strontium鍶

769 1 384 2.60

Barium鋇

725 1 640 3.51

Radium鐳

700 1 137 —

Similarities of Group II elements

1 They all have relatively low melting and boiling points when compared with other metals (except Group I metals).

2 They all have low densities.

3 They are all reactive metals and react readily with dilute hydrochloric acid to give hydrogen gas.

第 II族元素相似的性質

1 與其他金屬相比（第 I族金屬除外），第 II族元素的熔點和沸點都較低。

2 它們具有低密度。

3 它們都是活潑的金屬，會與稀氫氯酸穩定地反應，釋出氫氣。

25


4 They all react with non-metals to form compounds called salts.

Differences in reactivity of Group II elements

Group II elements are less reactive than Group I elements. The reactivity increases as we move down the group.

4 它們會與非金屬反應，生成稱為鹽的化合物。

第 II族元素活潑性的差異

第 II族元素的活潑性低於第 I族元素。元素的活潑性由上至下依次遞增。

Fig. 6.3 A summary of trends of some physical properties and reactivity of Groups I and II elements 第 I 與第 II 族元素的一些物理性質和活潑性的變化趨勢

Fr Ra

Cs Ba

Rb Sr

K Ca

Na Mg

Li Be

• melting and boiling points increasing熔點和沸點遞增

• reactivity decreasing活潑性遞減

• melting and boiling points decreasing熔點和沸點遞減

• reactivity increasing活潑性遞增

GroupI

第 I族

GroupII

第 II族

portion o t e periodic table is s own below.以下是週期表的其中一部分。

Li Be

Na Mg

K Ca

B C N O F Ne

Al Si P S Cl Ar

HHe





GroupI

第 I族

GroupII

第 II族

GroupIII

第 III族

GroupIV

第 IV族

GroupV

第 V族

GroupVI

第 VI族

GroupVII

第 VII族

Group0

第 0族


26

a) Describe the trend in reactivity down Group I when the elements react with water. 根據第 I族元素與水的反應，描述該族元素的活潑性由上至下的變化趨勢。

b) Explain why sodium is stored in paraffin oil. 為甚麼要把鈉貯存在石蠟油中？

c) In which way are the electronic arrangements of atoms of magnesium and calcium 比較鎂原子與鈣原子的電子排佈，

i) similar to each other? 有甚麼相同之處？

ii) different from each other? 有甚麼不同之處？

d) Potassium and magnesium are added separately to cold water in troughs. State TWO differences in the observations you expect.

現分別把鉀和鎂放入兩個盛有冷水的水槽裏，它們均會與冷水反應。舉出觀察結果上的兩項不同之處。

6.6 Group VII elements — halogens (P.44)

Group VII of the periodic table consists of the non-metals of fluorine, chlorine, bromine, iodine and astatine. These elements react with most metals to form salts. Hence they are called the halogens (which mean salt formers).

There is a gradual change in state as we move down the group. Fluorine and chlorine are gases, bromine is a liquid, and iodine is a solid at room temperature and pressure. There is also a gradual change in the intensity of colour, from pale yellow to black.

6.6 第 VII族元素 — 鹵素

第 VII族的元素是非金屬，分別是氟、氯、溴、碘和砹。這些元素能與大部分的金屬反應生成鹽，因此，它們稱為鹵素（「能生成鹽」之意）。

元素的狀態由上至下依次遞變：在常温常壓下，氟和氯是氣體，溴是液體，碘則是固體。元素顏色的深度也依次遞變，由淺黃色漸變至黑色。

Table 6.6 Some physical properties of the first four Group VII elements首四種第 VII族元素的一些物理性質

Element元素


Colour顏色



Fluorine氟

gas氣體

pale yellow淺黃

–220 –190

Chlorine氯

gas氣體

greenish yellow黃綠

–101 –34

Bromine溴

liquid液體

reddish brown紅棕

–7 58

Iodine碘

solid固體

black黑

113 184

27


Similarities in properties of Group VII elements

1 They are all poisonous and smelly.

2 They are all non-metals.

3 They all react with metals to form compounds called salts.

Differences in reactivity of Group VII elements

The reactivity of these elements decreases as we move down the group.

6.7 Group 0 elements — noble gases (P.46)

The six elements in Group 0 are helium, neon, argon, krypton, xenon and radon. They are called noble gases because they rarely react with other substances.

The melting point, boiling point and density of the elements increase as we move down the group.

第 VII族元素相似的性質

1 它們都具毒性和難聞的氣味。

2 它們都是非金屬。

3 它們會與金屬反應，生成稱為鹽的化合物。

第 VII族元素活潑性的差異

鹵素的活潑性由上至下依次遞減。

6.7 第 0族元素 — 貴氣體

第 0族的六種元素分別是氦、氖、氬、氪、氙和氡。它們甚少與其他物質反應，所以稱為貴氣體。

這些元素的熔點、沸點和密度由上至下依次遞增。

Table 6.7 Some physical properties of the Group 0 elements第 0族元素的一些物理性質

Element元素





Helium氦

gas氣體

–270 –269 0.000179

Neon氖

–249 –246 0.000900

Argon氬

–189 –186 0.00178

Krypton氪

–157 –152 0.00373

Xenon氙

–112 –107 0.00589

Radon氡

–71 –62 0.00973

Similarities in properties of Group 0 elements

1 They are all colourless gases at room temperature and pressure.

2 They all have very low melting and boiling points.

3 They are all very unreactive.

第 0族元素相似的性質

1 在常温常壓下，它們都是無色的氣體。

2 它們具有甚低的熔點和沸點。

3 它們都極不活潑。


28

Stability of Group 0 elements

The octet rule suggests that atoms become stable by having eight electrons in their outermost shells (or two electrons in the case of some smaller atoms). We say that these atoms have an octet structure in their outermost shells (or a duplet structure in the case of two electrons).

Uses of Group 0 elements

第 0族元素的穩定性

八隅體規則指出如果原子的最外電子層具有 8個電子，便能達致穩定（一些較細小的原子則只需 2個電子）。我們說這些原子的最外電子層具八隅體結構（如果只具 2個電子，則稱為電子偶結構）。

第 0族元素的用途

Table 6.8 The uses of three Group 0 elements三種第 0族元素的用途

Noble gas貴氣體

Use(s)用途

Reason(s)使用原因

Helium氦

• in balloons and airships 用於氣球和氣船

• low density 密度低• unreactive 不活潑

Neon氖

• in advertising signs 用於廣告燈箱

• glows red when an electric current is passed through it 電流流經氖時，氖會發出耀目的紅光

Argon氬

• filling electric light bulbs 充填電燈泡

• does not react with the metal filament in a light bulb 不會與燈泡內的燈絲產生反應

Fig. 6.4 Helium is used in party balloons

氦可用來充填氣球

Fig. 6.5 Neon is used in advertising signs

氖可用於霓虹燈 Fig. 6.6 Argon is used to fill electric light bulbs

氬可用於充填電燈泡

29


The table below lists the atomic numbers of four elements, W, X, Y and Z.下表列出四種元素，W、X、Y及 Z的原子序。

Element元素


W 9

X 10

Y 17

Z 20

a) Suggest an element with an atom that has an octet structure in the outermost shell. 舉出其中的一種元素，其原子的最外電子層具有八隅體結構。

b) Two of the elements show similar chemical properties. 上表中有兩種元素具有相似的化學性質。

i) Identify the elements. 指出這兩種元素。

ii) Explain why the two elements show similar chemical properties. 解釋為甚麼這兩種元素具有相似的化學性質。

iii) Suggest ONE reaction in which both elements behave similarly. 舉出一項這兩種元素都會進行的化學反應。

6.8 Predicting the chemical properties of unfamiliar elements (P.50)

We can use the periodic table to predict chemical properties of unfamiliar elements as well. For example, sodium and potassium are Group I elements. Both of them react with water vigorously. Rubidium belongs to the same group. Therefore we expect it to react with water vigorously as well.

6.8 預測陌生元素的化學性質

我們可以用週期表來推測一些陌生的元素的化學性質。例如鈉和鉀是第 I族元素，它們與水反應時十分劇烈。銣也屬於同一族。因此，我們預期它與水反應時也會十分劇烈。


30

1 Mendeléev knew that silicon tetrachloride (SiCl4) existed. Using his periodic table, he correctly predicted the existence of ekasilicon, an element just below silicon in the periodic table.

門德列夫知道有四氯化硅（S iC l4）這種化合物。此外，他利用他的週期表準確地預測一種稱為類硅的元素存在。在週期表中，類硅位於硅之下。

Predict the chemical formula of the compound formed between ekasilicon and chlorine. 推測類硅與氯反應時生成的化合物的化學式。

2 A, B and C are three different elements belonging to the same group. The electronic arrangements of their atoms are as follows:

A、B及 C是三種不同的元素，它們屬於同一族。它們的原子的電子排佈如下：

Element元素


A 2,8,2

B 2,8,8,2

C p,q,18,8,r

a) Name the group of elements to which they belong. 說出它們屬於哪一族。

b) What are the numerical values for p, q and r in the electronic arrangement of an atom of C? 在 C的原子的電子排佈中，p、q和 r的數值是多少？

c) Predict the state of element C at room temperature and pressure. 推測元素 C在常温常壓下的狀態。

d) Predict which of the elements would react most vigorously with water. Explain your answer. 推測哪種元素與水的反應最劇烈。試解釋之。

31


6.9 From atoms to ions (P.52)

Atoms can obtain the stable electronic arrangements of atoms of noble gases by gaining or losing electrons.

Positive ions — cations

6.9 由原子變成離子

原子藉着獲得或失去電子，可以獲得貴氣體原子的穩定電子排佈。

正離子 — 陽離子

A simple ion forms when an atom either loses or gains one or more electrons. It is either positively or negatively charged.

原子失去或獲得一個或以上的電子時，便會形成離子。離子會帶正電荷或負電荷。

When a sodium atom loses an electron, a sodium ion forms. The ion has 11 protons but 10 electrons only. It has one more positive charge than negative charge. Therefore the sodium ion is positively charged. It is a positive ion (i.e. a cation).

當鈉原子失去一個電子，便會形成鈉離子。鈉離子具有 11個質子，但只有 10個電子。它帶的正電荷比負電荷多一個，所以鈉離子帶正電荷，它是一個正離子（即陽離子）。

Fig. 6.7 A sodium atom loses 1 electron to form a sodium ion with 1 positive charge 鈉原子失去一個電子後，會形成帶一個正電荷的鈉離子


sodium ion鈉離子

+ e–

+

11p12n

11p12n

A sodium ion carries 1 positive charge and is represented by the symbol Na+. The ‘+’ sign means 1 positive charge.

鈉離子帶一個正電荷，可以Na+

表示。「+」表示一個正電荷。

When an atom of an element loses one or more electrons, it forms a positive ion. A positive ion is called a cation.

元素的原子失去一個或以上的電子時，會形成正離子。正離子稱為陽離子。

An atom of a metal can obtain the stable electronic arrangement of an atom of a noble gas by losing one or more electrons.

金屬的原子藉着失去一個或以上的電子，可以獲得像貴氣體原子的穩定電子排佈。


32

Negative ions — anions

An atom of a non-metal can obtain the stable electronic arrangement of an atom of a noble gas by gaining one or more electrons.

When a chlorine atom gains an electron, a chloride ion forms. The ion has 17 protons but 18 electrons. It has one more negative charge than positive charge. Therefore the chloride ion is a negative ion (i.e. an anion).

A chloride ion carries 1 negative charge and is represented by the symbol Cl–. The ‘–’ sign means 1 negative charge.

負離子 — 陰離子

非金屬的原子藉着獲得一個或以上的電子，可以獲得貴氣體原子的穩定電子排佈。

當氯原子獲得一個電子，便會形成氯離子。氯離子具有 17個質子和 18個電子。它帶的負電荷比正電荷多一個，所以氯離子是一個負離子（即陰離子）。

氯離子帶一個負電荷，可以 Cl–

表示。「–」表示一個負電荷。

When an atom of an element gains one or more electrons, it forms a negative ion. A negative ion is called an anion.

當元素的原子獲得一個或以上的電子，便會形成負離子。負離子稱為陰離子。

An atom of a non-metal can obtain the stable electronic arrangement of an atom of a noble gas by gaining one or more electrons.

非金屬的原子藉着獲得一個或以上的電子，可以獲得貴氣體原子的穩定電子排佈。

Fig. 6.8 A chlorine atom gains 1 electron to form a chloride ion with 1 negative charge 氯原子獲得一個電子後，會形成帶一個負電荷的氯離子

chlorine atom氯原子

+ e–17p18n

chloride ion氯離子

–

17p18n

6.10 Predicting the charge on an ion (P.55)

Atoms of Group I elements lose one electron so as to obtain the electronic arrangements of atoms of noble gases. Ions with 1 positive charge are formed.

For atoms of non-metals in Group V, VI and VII, they gain ‘8 – group number’ electrons in order to obtain the stable electronic arrangements of atoms of noble gases. For example, atoms of Group VI elements form ions with 2 (8 – 6) negative charges.

6.10 預測離子所帶的電荷

第 I族元素的原子失去一個電子，獲得貴氣體的原子的電子排佈，形成帶一個正電荷的陽離子。

第 V、VI和 VII族的非金屬的原子要獲得「8 –族數」的電子，才能獲得貴氣體的原子的電子排佈。例如第 VI族元素的原子形成的離子帶兩個負電荷（8 – 6）。

33


Positive charge(s) on an ion formed from the atom of a metal = group number of the metal

Negative charge(s) on an ion formed from the atom of a non-metal = 8 – group number of the non-metal

由金屬的原子形成的離子所帶的正電荷 = 該金屬的族數

由非金屬的原子形成的離子所帶的負電荷 = 8 – 該非金屬的族數

1 Consider the element magnesium. 考慮鎂這種元素。

a) Draw an electron diagram of a magnesium atom. 繪出鎂原子的電子圖。

b) How can a magnesium atom obtain the electronic arrangement of an atom of a noble gas? 鎂原子怎樣才能達到像貴氣體原子般的電子排佈？

c) Draw an electron diagram of a magnesium ion. 繪出鎂離子的電子圖。

d) Suggest the charge on a magnesium ion. 指出鎂離子所帶的電荷。

2 Consider the following ions: 就下列每個離子，

At–, Ba2+, Cs+, Ga3+, P3–, Se2–

For each ion, state in which group of the periodic table you would expect to find the element which forms the ion.

指出它是由週期表中哪一族的元素形成的。

3 X is an element. It can form a cation X+ with an electronic arrangement of 2,8,8. To which period of the periodic table does X belong? Explain your answer.

X是一種元素，它可以形成一個電子排佈為 2,8,8的陽離子 X +。指出 X屬於週期表中的哪一週期，並加以解釋。


34

族 g

週期 p

活潑性 r

鹼金屬 a m

鹼土金屬 a e m

鹵素 h

貴氣體 n g

八隅體規則 o r

電子偶 d

陽離子 c

陰離子 a

35


1 In the periodic table, all the elements are arranged in order of increasing

.

2 The vertical columns in the periodic table are called , which are numbered from

to , followed by Group (or Group ).

Group number of an element = number of in an atom of the

element

3 The horizontal rows in the periodic table are called .

Period number of an element = number of in an atom of the

element

4 Across a period in the periodic table, the elements change from metals through

to .

5 a) Elements in the same group have the same number of in

their atoms and thus they have similar .

b) There is usually a gradual change in the of elements as we move down a

group.

6 Group I elements — alkali metals

a) They all have relatively melting and boiling points when compared with

other metals.

b) They are all and can be cut with a knife.

c) They all have — lithium, sodium and potassium fl oat on

water.

d) They are all metals and must be stored in

to prevent them from reacting with air.


36

e) They all react vigorously with water to give gas and an

solution.

f) They all react with non-metals to form compounds called .

g) The reactivity of these elements as we move down the group.

7 Group II elements — alkaline earth metals

a) They all have relatively melting and boiling points when compared with

other metals (except Group I metals).

b) They all have densities.

c) They are all metals and react readily with

to give hydrogen gas.

d) They all react with to form compounds called salts.

e) Group II elements are reactive than Group I elements. The reactivity

as we move down the group.

8 Group VII elements — halogens

a) They are all and .

b) They are all .

c) They all react with to form compounds called salts.

d) The reactivity of these elements as we move down the group.

37


9 The following diagram shows the trends of some physical properties and reactivity of Groups I, II

and VII elements.

Fr Ra

Cs Ba

Rb Sr

K Ca

Na Mg

Li Be

I

Br

Cl

F

• melting and boiling points

• reactivity


• reactivity

GroupI

GroupII

GroupVII


• reactivity

10 Group 0 elements — noble gases

a) They are all gases at room temperature and pressure.

b) They all have very melting and boiling points.

c) They are all very .

11 The suggests that atoms become stable by having eight

electrons (an octet structure) in their outermost shells (or two electrons, a duplet structure, in the

case of some smaller atoms).

12 Atoms can obtain the stable electronic arrangements of atoms of noble gases by gaining or losing

electrons.

loses electron(s) atom of positive ion (or )

gains electron(s) atom of negative ion (or )


38

13 a) Positive charge(s) on an ion formed from the atom of a metal

=

b) Negative charge(s) on an ion formed from the atom of a non-metal

= –

39

Unit 7 Ionic and metallic bonds 離子鍵及金屬鍵

Unit 7 Ionic and metallic bonds (P.68)

7.1 Conductors, electrolytes and non-conductors (P.68)

Conductors

These are substances which conduct electricity but are not chemically changed during conduction. For example, metals are conductors.

Electrolytes

These are compounds which conduct electricity in molten state or aqueous solution. They are decomposed by electricity during conduction. Compounds made up of metals and non-metals are electrolytes.

第 7節離子鍵及金屬鍵

7.1 導電體、電解質及非導電體

導電體

這些物質可導電，但在導電過程中不會產生化學變化。例如金屬是導電體。

電解質

這些是在熔融或水溶液狀態時才能導電的化合物，它們在導電的過程中會被電流分解。由金屬和非金屬組成的化合物是電解質。

Fig. 7.1 Classification of substances according to how they conduct electricity 把物質按其導電性分類

substances物質

conductors導電體

electrolytes電解質

non-conductors非導電體

compounds化合物

• distilled water (made up of hydrogen and oxygen)蒸餾水（成分元素有氫與氧）

• ethanol (made up of carbon, hydrogen and oxygen)乙醇（成分元素有碳、氫與氧）

• sugar (made up of carbon, hydrogen and oxygen)糖（成分元素有碳、氫與氧）

non-metals非金屬

• carbon (diamond) 碳（鑽石）

• chlorine 氯

• sulphur 硫

• copper銅

• magnesium 鎂

• iron 鐵

• sodium chloride (made up of sodium and chlorine)氯化鈉（成分元素有鈉與氯）

• lead(II) bromide (made up of lead and bromine) 溴化鉛(II)（成分元素有鉛與溴）

• potassium iodide (made up of potassium and iodine)碘化鉀（成分元素有鉀與碘）

Examples例子


40

Non-conductors

These are substances which do not conduct electricity in solid, molten state or aqueous solution. All non-metals (except graphite) are non-conductors. Compounds made up of non-metals are also non-conductors.

7.2 Evidence of ions from electrolysis of molten lead(II) bromide (P.69)

When we pass electricity through the molten lead(II) bromide, a reddish brown gas (bromine) is formed at the positive electrode. A white shiny solid (lead) is formed at the negative electrode. Lead(II) bromide is decomposed into lead and bromine by electricity.

To explain the observations, we assume that lead(II) bromide is made up of positive lead(II) ions (Pb2+) and negative bromide ions (Br–).

非導電體

這些物質無論在固體、熔融狀態還是溶於水時都不會導電。除了石墨外，所有非金屬都是非導電體，由非金屬組成的化合物也是非導電體。

7.2 從電解溴化鉛 (II)獲得離子存在的證據

當我們把電流通過熔融的溴化鉛 (II)，紅棕色的氣體（溴）會在正電極生成，銀白色的固體（鉛）則在負電極生成。電流將溴化鉛 (II)分解成鉛和溴。

要解釋這個現象，可假設溴化鉛 (II)是由帶正電荷的鉛 (II)離子（Pb2+）和帶負電荷的溴離子（Br–）所組成。

Fig. 7.2 Explaining what happens during the electrolysis of molten lead(II) bromide 電解熔融溴化鉛(II)時產生的變化

• Bromide ions carrying negative charges move towards the positive electrode.

帶負電荷的溴離子移向正電極。• Lead(II) ions carrying positive charges move towards the negative

electrode. 帶正電荷的鉛 (II)離子移向負電極。

–+Br–

Br–

Br–Br–

Pb2+

Pb2+

At the positive electrode在正電極上產生的變化

• Each bromide ion gives up one electron to the electrode and becomes a bromine atom. Bromine atoms then join in pairs to form bromine molecules.

每個溴離子失去一個電子，變成溴原子。溴原子接着以一對一對的形式連結在一起，形成溴分子。 bromide ions – electrons bromine atoms bromine

molecules 溴離子 – 電子溴原子溴分子

Br–

Br–

Br–

Br–Pb2+

–+e–

e–

Pb2+

At the negative electrode在負電極上產生的變化

• Each lead(II) ion receives two electrons from the electrode and becomes a lead atom.

每個鉛 (II)離子從電極獲得兩個電子，變成鉛原子。 lead(II) ions + electrons lead atoms 鉛 (II)離子 + 電子鉛原子

Br–

Br–

–+e–

e–

Pb2+

Br BrPb2+

41


In solid state, ions in the compound are held together by strong attraction. They are not free to move. Hence solid lead(II) bromide does not conduct electricity.

When lead(II) bromide becomes molten, the lead(II) ions and bromide ions become mobile.

7.3 Chemical bonds (P.71)

We have learnt that elements combine to form compounds. The particles in these compounds are held together by chemical bonds. A chemical bond is a force that holds the particles together.

7.4 Ionic bonds (P.71)

Ionic bond in sodium chloride

When a sodium atom loses one electron, it forms a sodium ion with 1 positive charge.

在固態時，化合物內的離子由強大的吸引力連結在一起，不能自由流動。因此，固態的溴化鉛 (II)不能導電。

當溴化鉛 (II)熔化，鉛 (II)離子和溴離子便可自由流動。

7.3 化學鍵

我們知道化合物由不同的元素結合而成，這些化合物內的粒子化學鍵連結在一起。化學鍵是把這些粒子連結在一起的引力。

7.4 離子鍵

氯化鈉中的離子鍵

當鈉原子失去一個電子，會形成帶一個正電荷的鈉離子。

Fig. 7.3 Formation of a sodium ion 鈉離子的形成

Fig. 7.4 Formation of a chloride ion 氯離子的形成


+ e–

sodium ion鈉離子

+

Na Na

When a chlorine atom gains one electron, it forms a chloride ion with 1 negative charge.

當氯原子獲得一個電子後，會形成帶一個負電荷的氯離子

Cl


+ e–

–

Cl



42

When sodium and chlorine react, the electron released by the sodium atom is accepted by the chlorine atom. The compound sodium chloride is produced.

鈉與氯反應時，鈉原子放出的電子都由氯原子接收，生成的化合物是氯化鈉。

Fig. 7.5 Electron transfer during the reaction between sodium and chlorine 鈉和氯反應時原子間的電子轉移

Na NaCl Cl

+ –



sodium ion鈉離子


The positively charged sodium ion is attracted to the negatively charged chloride ion by electrostatic forces. This attraction, which holds the ions together, is a chemical bond called an ionic bond. A compound with such a bond is called an ionic compound.

帶正電荷的鈉離子藉着靜電力被帶負電荷的氯離子吸引。這種連結離子的引力，是一種稱為離子鍵的化學鍵。具有這種化學鍵的化合物稱為離子化合物。

An ionic bond is the strong electrostatic forces of attraction between oppositely charged ions.

離子鍵是具相反電荷的離子之間的強大的靜電力。

An ionic bond is formed when one or more electrons are transferred from one atom (or group of atoms) to another.

當一個或以上的電子從一個原子（或一組原子）轉移到另一個原子（或另一組原子）時，便形成離子鍵。

When a metal and a non-metal combine to form an ionic compound, atoms of the metal release electrons while atoms of the non-metal gain electrons.

當金屬與非金屬化合生成離子化合物，金屬的原子會放出電子，非金屬的原子會獲得電子。

Ionic bond in magnesium fl uoride

A magnesium atom tends to lose two electrons to obtain the electronic arrangement of a stable neon atom. The magnesium ion is represented by the symbol Mg2+.

氟化鎂中的離子鍵

鎂原子傾向失去兩個電子，以獲得氖原子的電子排佈，可以Mg2+表示鎂離子。

43


Fig. 7.6 Formation of a magnesium ion 鎂離子的形成

Fig. 7.7 Formation of a fluoride ion 氟離子的形成

Fig. 7.8 Electron transfer during the reaction between magnesium and fluorine 鎂和氟反應時原子間的電子轉移

magnesium atom鎂原子

+ 2 e–

magnesium ion鎂離子

2+

Mg Mg

F

fluorine atom氟原子

+ e–

–

F

fluoride ion氟離子

F


F


magnesium atom鎂原子

Mg


Mg

2+

–

F


–

F


A fl uorine atom tends to gain one electron to obtain the electronic arrangement of a stable neon atom. The fl uoride ion is represented by the symbol F–.

氟原子傾向獲得一個電子，以獲得氖原子的電子排佈，可以 F–表示氟離子。

When magnesium and fl uorine react, the two electrons released by the magnesium atom are accepted by two fl uorine atoms. The two negatively charged fl uoride ions are attracted to the positively charged magnesium ion. Ionic bonds are formed between the magnesium and fluoride ions. The compound magnesium fl uoride is produced.

鎂和氟反應時，鎂原子放出的兩個電子會被兩個氟原子接收。兩個帶負電荷的氟離子會被帶正電荷的鎂離子吸引，鎂離子與氟離子之間形成離子鍵，生成的化合物是氟化鎂。


44

Ionic bond in lithium oxide

A lithium atom tends to lose one electron to obtain the electronic arrangement of a stable helium atom. The lithium ion is represented by the symbol Li+.

氧化鋰中的離子鍵

鋰原子傾向失去一個電子，以獲得氦原子穩定的電子排佈，可以 Li+

表示鋰離子。

Fig. 7.9 Formation of a lithium ion 鋰離子的形成

Fig. 7.10 Formation of an oxide ion 氧離子的形成

Fig. 7.11 Electron transfer during the reaction between lithium and oxygen 鋰和氧反應時原子間的電子轉移

+ e–

lithium ion鋰離子

+

lithium atom鋰原子

Li Li

O

oxygen atom氧原子

+ 2 e–

2–

oxide ion氧離子

O

+

+

2–


Li


Li


Li


Li

O

oxygen atom氧原子

O

oxide ion氧離子

An oxygen atom tends to gain two electrons to obtain the electronic arrangement of a stable neon atom. The oxide ion is represented by the symbol O2–.

When lithium and oxygen react, two lithium atoms are required to release the two electrons needed by the oxygen atom. Two positively charged lithium ions are attracted to the negatively charged oxide ion. Ionic bonds are formed between the lithium and oxide ions. The compound lithium oxide is produced.

氧原子傾向獲得兩個電子，以獲得氖原子的電子排佈，可以 O2–

表示氧離子。

鋰與氧反應時，需要兩個鋰原子來放出氧原子所需的電子。兩個帶正電荷的鋰離子會被帶負電荷的氧離子吸引，鋰離子與氧離子之間形成離子鍵，生成的化合物是氧化鋰。

45


1 Use an electron diagram to show the electron transfer when each of the following pairs of elements react. 以電子圖展示下列兩對元素反應時原子間的電子轉移。

a) sodium and sulphur 鈉和硫

b) calcium and nitrogen 鈣和氮

2 The following table shows the atomic numbers of four elements. 下表列出四種元素的原子序。

Element元素

a b c d


2 14 17 19

a) Which TWO elements would form an ionic compound? 哪兩種元素會反應生成離子化合物？

b) Draw an electron diagram of the compound formed. 繪出這離子化合物的電子圖。

7.5 Compounds containing polyatomic ions (P.75)

An ion can also be formed from a group of atoms. This is called a polyatomic ion.

7.5 含多原子離子的化合物

離子也可以是由一組原子組成的，這些離子稱為多原子離子。

Table 7.1 Examples of polyatomic ions多原子離子的例子

Name離子名稱

Hydroxide氫氧離子

Nitrate硝酸根離子

Carbonate碳酸根離子

Sulphate硫酸根離子

Ammonium銨離子

Chemical formula化學式

OH– NO3– CO3

2– SO42– NH4

+

Model離子的模型

O HO

NO O

O

CO O O O

O

S

OH H

N

H

H

Ionic compounds may contain positive metal ions bonded to negative polyatomic ions.

離子化合物可能包含與帶負電荷的多原子離子鍵合的帶正電荷的金屬離子。


46

7.6 Name of ions (P.76)

Names of positive ions

If a metal forms only one kind of positive ion, the name of the ion is the same as the metal. For example, potassium (K) forms potassium ion (K+).

7.6 離子的名稱

正離子的名稱

如果金屬只可以形成一種正離子，離子的名稱和金屬的一樣。例如鉀原子（K）形成鉀離子（K+）。

Table 7.2 Names of some common positive ions一些常見的陽離子的名稱

With 1 positive charge帶一個正電荷

With 2 positive charges帶兩個正電荷

With 3 positive charges帶三個正電荷


Name離子名稱


Name離子名稱


Name離子名稱

Li+ lithium ion鋰離子

Mg2+ magnesium ion鎂離子

Al3+ aluminium ion鋁離子

Na+ sodium ion鈉離子

Ca2+ calcium ion鈣離子

Fe3+ iron(III) ion鐵 (III)離子

K+ potassium ion鉀離子

Zn2+ zinc ion鋅離子

Ag+ silver ion銀離子

Fe2+ iron(II) ion鐵 (II)離子

H+ hydrogen ion氫離子

Cu2+ copper(II) ion銅 (II)離子

NH4+ ammonium ion

銨離子Pb2+ lead(II) ion

鉛 (II)離子

Cu+ copper(I) ion銅 (I)離子

Some metals can form more than one kind of positive ion. For example, copper can form two kinds of positive ions, one carrying 1 positive charge and one carrying 2 positive charges (Cu+ and Cu2+). When naming these ions, write a Roman numeral in brackets after the name of the metal to show the number of positive charges. Thus, we use the name of copper(I) ion for Cu+, and copper(II) ion for Cu2+.

有些金屬可以形成多於一種的正離子。例如銅原子可以形成兩種正離子，一種帶有一個正電荷，另一種則帶有兩個正電荷（Cu+和Cu2+）。命名這些離子時，要在金屬名稱後加上羅馬數字，並加上括號，表示該離子所帶的正電荷的數目。所以我們稱 Cu+為銅 (I)離子，Cu2+為銅 (II)離子。

47


Names of negative ions

Negative ions include all simple non-metal ions (except H+) and most polyatomic ions.

負離子的名稱

負離子包括所有簡單的非金屬離子（H+除外）和大部分的多原子離子。

Table 7.3 Examples of metals that can form more than one kind of positive ion能形成多於一種陽離子的金屬的例子

Ion離子

Name of ion離子名稱

Example of compound化合物的例子

Cu+ copper(I) ion銅 (I)離子

copper(I) oxide氧化銅 (I)

Cu2+ copper(II) ion銅 (II)離子

copper(II) oxide氧化銅 (II)

Fe2+ iron(II) ion鐵 (II)離子

iron(II) chloride氯化鐵 (II)

Fe3+ iron(III) ion鐵 (III)離子

iron(III) chloride氯化鐵 (III)

Table 7.4 Names of some common negative ions一些常見的陰離子的名稱

With 1 negative charge帶一個負電荷

With 2 negative charges帶兩個負電荷

With 3 negative charges帶三個負電荷


Name離子名稱


Name離子名稱


Name離子名稱

F– fluoride ion氟離子

O2– oxide ion氧離子

N3– nitride ion氮離子

Cl– chloride ion氯離子

S2– sulphide ion硫離子

PO43– phosphate ion

磷酸根離子

Br– bromide ion溴離子

SO32– sulphite ion

亞硫酸根離子

I– iodide ion碘離子

SO42– sulphate ion

硫酸根離子

NO2– nitrite ion

亞硝酸根離子CO3

2– carbonate ion碳酸根離子

NO3– nitrate ion

硝酸根離子Cr2O7

2– dichromate ion重鉻酸根離子

OH– hydroxide ion氫氧離子

HCO3– hydrogencarbonate ion

碳酸氫根離子

HSO4– hydrogensulphate ion

硫酸氫根離子

MnO4– permanganate ion

高錳酸根離子


48

Simple negative ions have names ending in ‘-ide’. Polyatomic ions containing oxygen have names ending in -ite or -ate. The polyatomic ion with less oxygen is named -ite, and that with more oxygen is named -ate.

7.7 Naming ionic compounds (P.78)

When naming an ionic compound in English, name the positive ion fi rst, followed by the negative ion.

簡單陰離子的名稱以 -ide結尾。含氧的多原子離子的名稱以 -ite或 -ate結尾。含較少氧的以 -ite結尾；含較多氧的以 -ate結尾。

7.7 離子化合物的命名

以英文命名離子化合物時，先命名正離子，跟着是命名負離子。

Table 7.5 Names of some ionic compounds一些離子化合物的名稱

Positive ion in the compound化合物內的陽離子

Negative ion in the compound化合物內的陰離子

Name of the compound化合物名稱


oxide ion氧離子

lithium oxide氧化鋰



magnesium fluoride氟化鎂

ammonium ion銨離子


ammonium chloride氯化銨

calcium ion鈣離子

nitrate ion硝酸根離子

calcium nitrate硝酸鈣

copper(II) ion銅 (II)離子

carbonate ion碳酸根離子

copper(II) carbonate碳酸銅 (II)

iron(III) ion鐵 (III)離子

hydroxide ion氫氧離子

iron(III) hydroxide氫氧化鐵 (III)

iron(II) ion鐵 (II)離子

sulphate ion硫酸根離子

iron(II) sulphate硫酸鐵 (II)

potassium ion鉀離子

permanganate ion高錳酸根離子

potassium permanganate高錳酸鉀

7.8 Colours of ionic compounds (P.78)

If an ionic compound has colour, the colour may arise from either the negative or positive ion, or even from both ions.

Consider the colours of the aqueous solutions of potassium chloride and potassium dichromate. The aqueous solution of potassium chloride is colourless. Hence the potassium ions must be colourless. Since the aqueous solution of potassium dichromate is orange in colour, the orange colour must come from the dichromate ions.

7.8 離子化合物的顏色

如果一個離子化合物有顏色，顏色可能由負或正離子，甚至兩種離子產生。

考慮氯化鉀水溶液和重鉻酸鉀水溶液的顏色。氯化鉀水溶液是無色的，所以鉀離子一定是無色的。重鉻酸鉀水溶液是橙色的，所以橙色必定是來自重鉻酸根離子。

49


Table 7.6 Colours of some ions in aqueous solutions一些離子在水溶液中呈現的顏色

Ion離子


Colour顏色

Iron(II)鐵 (II)離子

Fe2+ pale green淺綠

Iron(III)鐵 (III)離子

Fe3+ yellow-brown棕黃

Copper(II)銅 (II)離子

Cu2+ blue or green藍或綠

Permanganate高錳酸根離子

MnO4– purple

紫

Dichromate重鉻酸根離子

Cr2O72– orange

橙

Chromium(III)鉻 (III)離子

Cr3+ green綠

Nickel(II)鎳 (II)離子

Ni2+ green綠

Manganese(II)錳 (II)離子

Mn2+ very pale pink (or colourless)極淺粉紅（或無色）

Colours of gemstones

The colours of gemstones are due to the presence of traces of coloured ions.

寶石的顏色

寶石的顏色主要來自其中微量的有色離子。

Table 7.7 Coloured ions in gemstones寶石所含的有色離子

Gemstone寶石

Colour顏色

Ion present所含的離子

Chemical formula of ion離子的化學式

green綠色

chromium(III)鉻 (III)離子

Cr3+

jade 翡翠

green綠色

chromium(III)鉻 (III)離子

Cr3+

emerald 綠寶石

Continued on next page


50

Gemstone寶石

Colour顏色

Ion present所含的離子

Chemical formula of ion離子的化學式

purple紫色

manganese(III)錳 (III)離子

Mn3+

amethyst 紫水晶

light green淺綠色

iron(II)鐵 (II)離子

Fe2+

peridot 橄欖石

yellow-brown棕黃色

iron(III)鐵 (III)離子

Fe3+

topaz 黃玉

greenish blue藍綠色

copper(II)銅 (II)離子

Cu2+

turquoise 綠松石

Movement of coloured ions

When we place a small crystal of potassium permanganate at the centre of a strip of fi lter paper moistened with tap water, we can see a purple spot slowly moving towards the positive electrode. This is because negative permanganate ions which are purple in colour move towards the positive electrode. Positive potassium ions move towards the negative electrode. However, we cannot see the potassium ions because they are colourless.

Electricity is passed through a gel containing copper(II) ions and dichromate ions. An orange colour appears near the positive electrode. This is because negative dichromate ions move towards the positive electrode.

有色離子的移動

當我們把一小粒高錳酸鉀晶體放在經水喉水濕潤的濾紙的中央，我們可以看見紫色點移向正電極，這是因為紫色帶負電荷的高錳酸根離子移向正電極。帶正電荷的鉀離子會移向負電極。可是，我們看不見鉀離子，因為它們無色。

電流通過含有銅 (II)離子和重鉻酸根離子的膠凝體時，正電極附近會呈橙色，這是因為帶負電荷的重鉻酸根離子移向正電極。

51


+ –

10 V d.c. power supply10 V 直流電源

purple spot (permanganate ions)

紫色點（高錳酸根離子）

original position of potassium permanganate crystal高錳酸鉀晶體原位

filter paper moistened with tap water經自來水浸濕的濾紙

microscope slide顯微鏡載片

+ –

24 V d.c. power supply24 V 直流電源

carbonelectrodes碳電極

dilutesulphuric

acid稀硫酸

a gel containing copper(II) ions and dichromate ions

含有銅 (II)離子和重鉻酸根離子的膠凝體

Fig. 7.12 Movement of permanganate ions when electricity is passed through 通電後高錳酸根離子的移動情況

Fig. 7.13 Movement of ions when electricity is passed through a gel containing copper(II) ions and dichromate ions 電流通過含有銅(II)離子和重鉻酸根離子的膠凝體時，離子的移動情況

A blue colour appears near the negative electrode. This is because positive copper(II) ions move towards the negative electrode.

負電極附近會呈藍色，這是因為帶正電荷的銅 (II)離子移向負電極。


52

7.9 Chemical formulae of ionic compounds (P.83)

A chemical formula is a way of representing a chemical substance using symbols and fi gures.

The chemical formula of an ionic compound shows:

• the types of ions present; and

• the ratio of one type of ion to the other.

7.9 離子化合物的化學式

化學式是以符號和數字表示化學物質的一種方法。

離子化合物的化學式顯示：

• 化合物含有哪種離子；及

• 化合物內各種離子的比例。

1 Topaz is yellow-brown in colour. Suggest the ion responsible for the colour. 黃玉呈棕黃色。舉出哪種離子令黃玉呈這種顏色。

2 A student used the following set-up to study the movement of ions. 某學生利用以下裝置探究離子的移動。

+ –

d.c. power supply直流電源

filter paper moistened with tap water經自來水浸濕的濾紙

microscope slide顯微鏡載片

A CB

The student placed a drop of copper(II) sulphate solution at A and a drop of orange solution at C. The two solutions would not react.

該學生把一滴硫酸銅 (II)溶液置於 A點，一滴橙色溶液置於 C點。這兩種溶液不會產生反應。

a) The orange colour of the solution at C is due to the anion present. Name the ion responsible for the colour.

置於 C點的橙色溶液含有橙色的陰離子，寫出該陰離子的名稱。

b) Electricity was passed through for some time. 通電一段時間後，

i) What would be the colour change at A? Explain your answer. A點的顏色會有甚麼變化？試解釋之。

ii) What would be the colour change at B? Explain your answer. B點的顏色會有甚麼變化？試解釋之。

53


Table 7.8 Steps for working out the chemical formulae of ionic compounds書寫離子化合物的化學式的步驟

Step步驟

Calcium oxide氧化鈣

Copper(II) hydroxide氫氧化銅 (II)

Iron(III) carbonate碳酸鐵 (III)

1 Write down the symbols of ions in the compound.

寫出化合物內各離子的符號。 Ca O Cu OH Fe CO3

2 Write down the number of charges of each ion on the top of each symbol.

在符號上方寫上該離子所帶的電荷。

2 2 Ca O

2 1 Cu OH

3 2 Fe CO3

3 Cross multiply the numbers and the symbols.

將符號和數值交叉相乘。

2 2 Ca O= Ca2 = O2

2 1 Cu OH= Cu1 = (OH)2

3 2 Fe CO3

= Fe2 = (CO3)3

4 Combine the symbols and simplify the ratio if necessary.

將符號組合。若有需要，簡化比例。

CaO(Simplify the ratioof 2 : 2 to 1 : 1.)

（將 2：2簡化為 1：1）

Cu(OH)2

(Omit the number of 1 for Cu.)

（數字「1」可略去）

Fe2(CO3)3

Writing chemical formulae of ionic compounds

We write the chemical formula of an ionic compound by combining the symbols of its positive and negative ions.

書寫離子化合物化學式

我們書寫離子化合物的化學式時，把正離子和負離子的符號結合。

1 Write down the names of the following compounds: 寫出下列化合物的名稱。

a) MgCl2 b) Fe2O3 c) Ca(OH)2

2 Work out the chemical formulae of the following compounds: 寫出下列化合物的化學式。

a) sodium sulphate b) copper(II) chloride c) ammonium carbonate 硫酸鈉氯化銅 (II) 碳酸銨

d) lead(II) hydroxide e) potassium nitrate f) potassium dichromate 氫氧化鉛 (II) 硝酸鉀重鉻酸鉀

3 M is an element in the third period of the periodic table. It forms a hydroxide which has the chemical formula M(OH)3. What is the chemical formula of the sulphate of M?

M是第三週期中的元素，它的氫氧化物的化學式是M(OH)3。寫出它的硫酸鹽的化學式。


54

7.10 Metallic bonds in metals (P.85)

In a piece of metal, the outermost shell electrons of each atom are not held tightly to the nucleus. Instead, they are free to move randomly in the piece of metal. We can regard the mobile electrons as a ‘sea’ of electrons. Thus, a piece of metal consists of positively charged ions surrounded by a ‘sea’ of electrons. The outermost shell electrons are said to be delocalized as they are not associated with a particular ion and can move around.

7.10 金屬內的金屬鍵

在金屬內，因為每個原子的最外層電子都不是很緊地被原子核抓着，它們可以在金屬內隨意地移動，我們可以把這些流動的電子看成一個「電子海」。故此在一片金屬中，帶正電荷的離子會被「電子海」包圍。這些最外層電子稱為離域電子，由於它們不會夥同某一個特定的離子，而是可以四處移動。

e– e– e– e–

e–

e–

e–e–

e–

e–

e–e–

e–

e–

A metallic bond is a type of bond in which positive metal ions are held together by a ‘sea’ of mobile electrons.

由流動電子組成的電子海把帶正電荷的金屬離子連結在一起的化學鍵稱為金屬鍵。

The attractive forces between the negatively charged electrons and the positively charged ions hold the particles of a metal together. This type of bonding is found only in metals and is called a metallic bond.

帶負電荷的電子與帶正電荷的離子之間的引力把金屬粒子連結在一起，這種鍵合形式只可以在金屬中找到，稱為金屬鍵。

Fig. 7.14 A piece of metal consists of positively charged ions surrounded by a ‘sea’ of electrons 在金屬內，「電子海」包圍着帶正電荷的金屬離子

55


導電體 c

電解質 e

非導電體 n – c

化學鍵 c b

離子鍵 i b

靜電力 e f

離子化合物 i c

多原子離子 p i

離域 d

金屬鍵 m b


56

1 Substances can be classifi ed as conductors, electrolytes and non-conductors.

non-metalsmetals

compounds made up of metals and non-metals

compounds made up of non-metals

2 An ionic bond is the strong of attraction between oppositely

charged ions.

a) An ionic bond is formed when one or more electrons are from one atom (or

group of atoms) to another.

b) When a metal and a non-metal combine to form an ionic compound, atoms of the metal

electrons while atoms of the non-metal electrons.

3 The table below shows electron diagrams of some common ionic compounds.

Ionic compound Electron diagram

Na Cl

+ –


57


Ionic compound Electron diagram

Mg

2+

–

F

–

F

+

+

2–Li

Li

O

4 A ion is formed from a group of atoms, instead of a single atom.

5 a) Naming positive ions:

i) I f a metal forms only one kind of posit ive ion, the name of the ion is the

as the metal.

ii) Some metals can form more than one kind of positive ion. For example, we use the name

of ion for Cu+, and ion for Cu2+.

b) Naming negative ions:

i) Simple negative ions have names ending in .

ii) Polyatomic ions containing oxygen have names ending in or

.

iii) The polyatomic ion with less oxygen is named , and that with more

oxygen is named .

iv) A polyatomic ion formed from an oxygen atom and a hydrogen atom is called a

ion.


58

6 When naming an ionic compound, name the ion first, followed by the

ion.

7 If an ionic compound has colour, the colour may arise from either the or

ion, or even from both ions.

8 The chemical formula of an ionic compound shows the types of ions present and the

of one type of ion to the other.

9 A is a type of bond in which positive metal ions are held together

by a ‘sea’ of mobile electrons.

59

Unit 8 Covalent bonds 共價鍵

Unit 8 Covalent bonds (P.96)

8.1 Covalent bonds (P.96)

Compounds made up of non-metals only behave very differently from ionic compounds. The different behaviour is due to the structures that result when nonmetallic atoms are held together by covalent bonds.

8.2 Covalent bonds in non-metallic elements (P.96)

Atoms of non-metallic elements can join together to form groups called molecules. When the same kind of atoms join together, they form a molecule of an element.

The hydrogen molecule

Each hydrogen atom can obtain the electronic arrangement of a helium atom by sharing its electron with another hydrogen atom. The shared pair of electrons is attracted by the positive nucleus of each atom, forming a covalent bond.

第 8節共價鍵

8.1 共價鍵

只是由非金屬組成的化合物的特性與離子化合物的截然不同，這個不同的表現是因為非金屬藉着共價鍵連結在一起時，所得的結構與離子化合物的不同。

8.2 非金屬元素中的共價鍵

非金屬元素的原子互相連結，形成稱為分子的組合。同一種元素的原子連結時，會形成該元素的分子。

氫分子

每個氫原子可與另一個氫原子共用其電子，可以獲得氦原子的電子排佈。所共用的一對電子被每個原子的正原子核吸引，形成共價鍵。

bond pair electrons鍵合電子對

hydrogen molecule 氫分子 (H — H)

H H+ H H

Fig. 8.1 Formation of covalent bond in a hydrogen molecule 氫分子內的共價鍵

A covalent bond is formed when one or more pairs of outermost shell electrons are shared between two atoms.

當一對或以上的最外層電子被兩個原子共用，便形成共價鍵。

A covalent bond is the strong electrostatic forces of attraction between the shared electrons and the two positively charged nuclei of the bonded atoms.

共價鍵是共用電子對與兩個鍵合原子帶正電荷的原子核之間強大的靜電力。

The pair of bonded hydrogen atoms is a hydrogen molecule. A molecule is a group of atoms which are held together by covalent bonds.

這對鍵合的氫原子就是一個氫分子。分子是一組藉着共價鍵連結在一起的原子。


60

Each hydrogen molecule consists of two hydrogen atoms. We can say hydrogen forms diatomic molecules. The chemical formula of hydrogen gas is H2.

The chemical formula of a substance made up of molecules is also called its molecular formula.

The chlorine molecule

Each chlorine atom can obtain the electronic arrangement of an argon atom by sharing one of its outermost shell electrons with another chlorine atom.

每個氫分子由兩個氫原子組成，我們說氫分子是雙原子分子，化學式是 H2。

由分子組成的物質的化學式亦稱為其分子式。

氯分子

每個氯原子與另一個氯原子共用它其中的一個最外層電子，可以獲得氬原子的電子排佈。

The pair of electrons shared between two atoms is called bond pair electrons.

兩個原子之間共用的電子對稱為鍵合電子對。

Cl Cl ClCl +

chlorine molecule 氯分子 (Cl — Cl)

lone pair electrons孤電子對

Fig. 8.2 Formation of covalent bond in a chlorine molecule (only electrons in the outermost shell are shown) 氯分子內的共價鍵（只顯示最外層的電子）

In a chlorine molecule, each chlorine atom has three electron pairs in the outermost shell that are not involved in the bonding.

The pair of electrons in the outermost shell that is not involved in bonding is called lone pair electrons.

位於最外電子層上而沒有參與鍵合的電子對稱為孤電子對。

在氯分子內，每個氯原子的最外電子層上都有三對沒有參與鍵合的電子對。

The oxygen molecule

Each oxygen atom can obtain the electronic arrangement of a neon atom by sharing two of its electrons with another oxygen atom.

氧分子

每個氧原子與另一個氧原子共用它的兩個電子，可以獲得氖原子的電子排佈。

Fig. 8.3 Formation of covalent bond in an oxygen molecule (only electrons in the outermost shell are shown) 氧分子內的共價鍵（只顯示最外層的電子）

OOO +

oxygen molecule 氧分子 (O = O)

O

61


Fig. 8.4 Formation of covalent bond in a nitrogen molecule (only electrons in the outermost shell are shown) 氮分子內的共價鍵（只顯示最外層的電子）

Fig. 8.5a Ball-and-stick models of a hydrogen molecule, a chlorine molecule, an oxygen molecule and a nitrogen molecule (left to right)

氫分子、氯分子、氧分子及氮分子的球棒模型（由左至右）

Fig. 8.5b Space-filling models of some molecules 一些分子的填空模型

The nitrogen molecule

Each nitrogen atom can obtain the electronic arrangement of a neon atom by sharing three of its electrons with another nitrogen atom.

氮分子

每個氮原子與另一個氮原子共用它的三個電子，可以獲得氖原子的電子排佈。

A bond in which one pair of electrons is shared between two atoms is called a single bond.

A bond in which two pairs of electrons are shared between two atoms is called a double bond.

A bond in which three pairs of electrons are shared between two atoms is called a triple bond.

兩個原子共用一對電子所形成的共價鍵稱為單鍵。

兩個原子共用兩對電子所形成的共價鍵稱為雙鍵。

兩個原子共用三對電子所形成的共價鍵稱為三鍵。

NNN +

nitrogen molecule 氮分子 (N ≡ N)

N

Molecular models

We can build models of the molecules. The simplest models are ball-and-stick models.

分子的模型

我們可以用模型表示分子。球棒模型是最簡單的模型。

Cl Cl O O N NH H

To get a more accurate idea of how close together the atoms in a molecule are, we use space-fi lling models.

如果要更加準確了解分子內原子如何互相緊貼，我們就利用填空模型。


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8.3 Covalent compounds (P.100)

A huge number of compounds also exist as molecules. In these compounds, atoms of different elements share electrons with each other.

The hydrogen chloride molecule

In order to obtain stable electronic arrangements, one hydrogen atom forms a single bond with one chlorine atom. A hydrogen chloride molecule forms. The chemical formula of hydrogen chloride is HCl.

8.3 共價化合物

很多化合物亦以分子形式存在。在這些化合物內，不同類元素的原子彼此共用電子。

氯化氫分子

要獲得穩定的電子排佈，一個氫原子會與一個氯原子形成單鍵，生成一個氯化氫分子。氯化氫的化學式是 HCl。

Fig. 8.6 Formation of a covalent bond in a hydrogen chloride molecule (only electrons in the outermost shells are shown)

氯化氫分子內的共價鍵（只顯示最外層的電子）

Cl

hydrogen chloride molecule氯化氫分子 (H — Cl)

+H H Cl

Hydrogen chloride is a covalent compound, as a covalent bond holds the two atoms together.

The tetrachloromethane molecule

In order to obtain stable electronic arrangements, one carbon atom forms a single bond with each of four chlorine atoms. A tetrachloromethane molecule forms. The chemical formula of tetrachloromethane is CCl4.

氯化氫是共價化合物，因為共價鍵把兩個原子連結在一起。

四氯甲烷分子

要獲得穩定的電子排佈，一個碳原子會與四個氯原子中的每個氯原子形成單鍵，生成一個四氯甲烷分子。四氯甲烷的化學式是 CCl4。

Fig. 8.7 Formation of covalent bonds in a tetrachloromethane molecule (only electrons in the outermost shells are shown)

四氯甲烷分子內的共價鍵（只顯示最外層的電子）

Cl

Cl

Cl

Cl

Cl ClCl ClC C

tetrachloromethane molecule四氯甲烷分子

Cll

( Cl — C — Cl )l

Cl

63


The water molecule

In order to obtain stable electronic arrangements, one oxygen atom forms a single bond with each of two hydrogen atoms. A water molecule forms. The chemical formula of water is H2O.

The carbon dioxide molecule

In order to obtain stable electronic arrangements, one carbon atom forms a double bond with each of two oxygen atoms. A carbon dioxide molecule forms. The chemical formula of carbon dioxide is CO2.

水分子

要獲得穩定的電子排佈，一個氧原子會與兩個氫原子中的每個氫原子形成單鍵，生成一個水分子。水的化學式是 H2O。

二氧化碳分子

要獲得穩定的電子排佈，一個碳原子會與兩個氧原子中的每個氧原子形成雙鍵，生成一個二氧化碳分子。二氧化碳的化學式是 CO2。

Fig. 8.8 Formation of covalent bonds in a water molecule (only electrons in the outermost shells are shown) 水分子內的共價鍵（只顯示最外層的電子）

H H HH O O

water molecule 水分子(H — O — H)

The ammonia molecule

In order to obtain stable electronic arrangements, one nitrogen atom forms a single bond with each of three hydrogen atoms. An ammonia molecule forms. The chemical formula of ammonia is NH3.

氨分子

要獲得穩定的電子排佈，一個氮原子會與三個氫原子中的每個氫原子形成單鍵，生成一個氨分子。氨的化學式是 NH3。

Fig. 8.9 Formation of covalent bonds in an ammonia molecule (only electrons in the outermost shells are shown) 氨分子內的共價鍵（只顯示最外層的電子）

H

H H H HN

ammonia molecule氨分子

(H — N — H)lH

N

H


64

Fig. 8.10 Formation of covalent bonds in a carbon dioxide molecule (only electrons in the outermost shells are shown) 二氧化碳分子內的共價鍵（只顯示最外層的電子）

CO O O C O

carbon dioxide molecule 二氧化碳分子(O = C = O)

Number of electrons contributed by an atom for sharing

The number of electrons contributed by an atom for sharing is equal to what that atom needs to obtain a stable electronic arrangement. For example, a hydrogen atom (1) needs one more electron to obtain the electronic arrangement of a helium atom (2), so it contributes 1 electron for sharing. A nitrogen atom (2,5) needs three more electrons to obtain the electronic arrangement of a neon atom (2,8), so it contributes 3 electrons for sharing.

原子提供作共用的電子數目

一個原子會提供來共用的電子數目，相等於該原子需要多少個電子才獲得穩定的電子排佈。例如氫原子（1）需要一個電子以獲得氦原子的電子排佈（2），它便會提供一個電子作共用；氮原子（2,5）需要三個電子以獲得氖原子的電子排佈（2,8），它便會提供三個電子作共用。

Table 8.1 Number of electron(s) contributed for sharing by atoms of Period 2 non-metals during covalent bond formation 第二週期中非金屬元素的原子形成共價鍵時會提供作共用的電子數目

Period 2 non-metal第二週期中的非金屬元素

C N O F


2,4 2,5 2,6 2,7

Number of electron(s) needed to obtain the electronic arrangement of a noble gas atom原子達到穩定的電子排佈所欠的電子數目

4 3 2 1

Number of electron(s) contributed for sharing原子會提供作共用的電子數目

4 3 2 1

1 Use an electron diagram to show the sharing of electrons in the compound formed from each of the following pairs of elements:

以電子圖展示下列每對元素的原子如何共用電子，以達到穩定的電子排佈。

a) hydrogen and sulphur b) phosphorus and chlorine 氫和硫磷和氯

2 Show the bonding in HCN using an electron diagram. 利用電子圖顯示在 HCN分子中的化學鍵。

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3 A compound formed between carbon and element X has the following structure: 由碳和元素 X組成的化合物的分子具以下結構：

X C X

(Only electrons in the outermost shells are shown.) （只顯示最外層的電子）

How many electrons are there in the outermost shell of an atom of X? Explain your answer. X的原子的最外電子層上有多少個電子？試解釋之。

Table 8.2 Steps for working out the chemical formulae of covalent compounds書寫共價化合物化學式的步驟

Step步驟

Compound formed from hydrogen and sulphur氫和硫生成的化合物

Compound formed from silicon and chlorine硅和氯生成的化合物

1 Write down the electronic arrangements of the atoms involved.

寫出化合物內各原子的電子排佈。

H S 1 2,8,6

Si Cl 2,8,4 2,8,7

2 Decide the number of electrons each atom needs to obtain a stable electronic arrangement. Write down the number on the top of each atom.

計算各原子需要多少個電子，才可達到穩定的電子排佈，並把數值寫在符號上方。

A hydrogen atom needs 1 electron, while a sulphur atom needs 2 electrons.氫原子需要一個電子，硫原子則需要兩個電子。 1 2 H S

A s i l i con atom needs 4 e l e c t r o n s , w h i l e a chlorine atom needs 1 electron.硅原子需要四個電子，氯原子則需要一個電子。 4 1 Si Cl

3 Decide the number of each type of atoms in one molecule (cross multiply the numbers and the symbols).

將符號和數值交叉相乘。

1 2 H S= H2 = S1

4 1 Si Cl= Si1 = Cl4

4 Combine the symbols and simplify the ratio if necessary. 將符號組合。若有需要，簡化比例。

H2S(Omit the number

of 1 for S.)（數字「1」可略去）

SiCl4

(Omit the numberof 1 for Si.)

（數字「1」可略去）

8.4 Writing chemical formulae of covalent compounds (P.106)

We can use the following steps to work out the chemical formulae of covalent compounds.

8.4 書寫共價化合物的化學式

我們可用以下步驟寫出共價化合物的化學式。


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8.5 Predicting the formation of ionic and covalent compounds (P.106)

8.5 推斷會生成離子化合物還是共價化合物

When a metal combines with a non-metal, an ionic compound forms.

When non-metals combine, a covalent compound forms.

金屬與非金屬化合時，會生成離子化合物。

非金屬化合時，會生成共價化合物。

1 Consider the following pairs of elements: 考慮下列每對元素：

a) oxygen and fluorine b) potassium and sulphur 氧和氟鉀和硫

For each pair of elements, 就每對元素，

i) predict the type of compound (ionic or covalent) formed when they combine; 推斷當它們化合時，生成的是離子化合物還是共價化合物；

ii) state the chemical formula of the compound; 寫出其化學式。

iii) name the compound. 寫出其名稱。

2 Consider the substances listed below: 考慮下列的物質：

ammonia, carbon dioxide, chlorine, neon, potassium chloride 二氧化碳、氨、氯、氖、氯化鉀

Diagrams I, II and III below show the arrangements of particles, which can be atoms, ions or molecules. For each diagram, choose from the above list ONE substance which has the arrangement of particles as shown below at room temperature and pressure.

圖 I、I I和 I I I展示某些物質中粒子的排佈，粒子可以是原子、離子或分子。就以下每幅圖，從上列的物質中選出一種在常温常壓下具有如圖所示的粒子排佈。

I IIIII

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8.6 Dative covalent bonding (P.109)

We have looked at a covalent bond in which each of the two atoms provides one electron to form the bond between them. However, it is possible for just one atom to provide both bonding electrons. This atom is called the donor atom, and the two electrons it provides come from a lone pair on that atom. The other atom in the bond is called the acceptor atom. This kind of bonding is called dative covalent bonding.

8.6 配位共價鍵

我們已看過的共價鍵，是由兩個原子各自提供一個電子來形成它們之間的鍵。可是，一對鍵合電子亦有可能只由一個原子提供，這個原子稱為給體原子，它提供的兩個電子其實是它的孤電子對。在鍵合中另外一個原子稱為受體原子，這種鍵合稱為配位共價鍵。

A dative covalent bond is a covalent bond in which the bond pair electrons are provided by the same atom.

配位共價鍵是一個共價鍵，其中的鍵合電子對由同一個原子提供。

NH3BF3 molecule

When gaseous ammonia (NH3) and gaseous boron trifl uoride (BF3) react together, a solid of the formula NH3BF3 is formed. In a boron trifl uoride molecule, the boron atom has only 6 outermost shell electrons and it needs two more electrons to attain the octet structure.

The nitrogen atom in the ammonia molecule acts as a donor and supplies the lone pair electrons to the boron atom, forming a dative covalent bond. As a result, the boron atom attains an octet structure.

NH3BF3分子

氨氣（NH3）與三氟化硼氣體（BF3）反應，會生成化學式為 NH3BF3的固體。在三氟化硼分子中，硼原子只有六個最外層電子，它需要兩個電子以獲得穩定的八隅體結構。

在這情況下，氨分子中的氮原子充當給體原子，提供孤電子對給硼原子，形成配位共價鍵，結果令硼原子獲得八隅體結構。

Fig. 8.11 Formation of a dative covalent bond in a NH3BF3 molecule: (a) electron diagram (b) single line representation NH3BF3 分子內的配位共價鍵：(a)電子圖 (b)鍵線圖

+H N H NB

F

F

F B

F

F

H

H

F

H

H

H N F

F

F

B+

H

H

H FN

F

F

B

(a)

(b)


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Fig. 8.12 Formation of a dative covalent bond in an ammonium ion: (a) electron diagram (b) single line representation 銨離子內的配位共價鍵：(a)電子圖 (b)鍵線圖

Fig. 8.13 Formation of a dative covalent bond in a hydroxonium ion or hydronium ion: (a) electron diagram (b) single line representation

水合氫離子內的配位共價鍵：(a)電子圖 (b)鍵線圖

+H H+N H N H

H

H

H

H

H HN +

(a)

H

H

H HN

(b)

+

+

+

Ammonium ion (NH4+)

A dative covalent bond is also formed when an ammonia molecule and a hydrogen ion combine to form an ammonium ion (NH4

+).The nitrogen atom in the ammonia molecule supplies the lone pair electrons to the hydrogen ion.

銨離子（NH4+）

當氨分子與氫離子結合生成銨離子（NH4

+），也有配位共價鍵形成。氨分子中的氮原子提供它的孤電子對給氫離子。

Hydroxonium ion (H3O+)

When a water molecule and a hydrogen ion combine to form an hydroxonium ion (H3O

+), the oxygen atom in the water molecule supplies a lone pair of electrons to the hydrogen ion.

+H H+Ｏ H O H

HH

H

H HO +

(a)

H

H HO

(b)

+

+

水合氫離子（H3O+）

當水分子與氫離子結合生成水合氫離子（H3O

+），水分子中的氧原子提供它的孤電子對給氫離子。

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1 When gaseous ammonia reacts with gaseous hydrogen chloride, a solid ammonium chloride is formed. Draw an electron diagram of ammonium chloride.

氨氣與氯化氫氣體反應時，會生成氯化銨固體。試繪出氯化銨的電子圖。

2 There is a dative covalent bond present in a HNO3 molecule. Draw an electron diagram of the molecule. 在硝酸分子（HNO3）中有一個配位共價鍵。試繪出這分子的電子圖。

8.7 Bonding in polyatomic ions (P.111)

In a polyatomic ion, a group of atoms is covalently bonded together. The group as a whole has an overall charge.

The carbonate ion has acquired two more electrons from one or two other atoms so that each atom in the ion obtains a stable electronic arrangement. So, it carries 2 negative charges.

8.7 多原子離子中的化學鍵

在多原子離子中，一組的原子藉着共價鍵連結在一起。整組帶有一個總電荷。

碳酸根離子從其他一個或兩個原子取得兩個電子，令離子中的每個原子獲得穩定的電子排佈。所以整個離子帶兩個負電荷。

2–

C

O O

O

electron from an external source外來電子

electron from an external source外來電子

Fig. 8.14 The sharing of electrons among atoms in a carbonate ion (only electrons in the outermost shells are shown) 碳酸根離子內的原子共用電子（只顯示最外層的電子）

8.8 Relative molecular mass and formula mass (P.113)

Relative molecular mass

Just as the relative atomic mass is used to describe the relative masses of atoms, the relative molecular mass is used to describe the relative masses of molecules.

8.8 相對分子質量與式量

相對分子質量

恰如相對原子質量被用來描述原子的相對質量，相對分子質量被用來描述分子的相對質量。


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Formula mass

Ionic compounds consist of cations and anions. Since ionic compounds do not contain molecules, we use formula mass to describe the relative masses of ionic compounds.

式量

離子化合物包含陽離子和陰離子。由於離子化合物不含分子，我們用式量來描述離子化合物的相對質量。

Relative molecular mass of an element or compound= sum of relative atomic masses of all atoms present in

one molecule of the element or compound

元素或化合物的相對分子質量= 該元素或化合物一個分子內所有原子的相對原子質量的總和

Formula mass of an ionic compound= sum of the relative atomic masses of all atoms

making up one formula unit of the compound

離子化合物的式量= 組成該化合物的一個化學式單位的所有原子的相對原子質量的總和

1 Calculate the formula mass or relative molecular mass of each of the following substances. 計算下列物質的式量或相對分子質量。

Substance物質


Relative atomic mass

相對原子質量

Formula mass /relative molecular mass式量 / 相對分子質量

Ammonia氨

NH3

N = 14.0 H = 1.0

Copper(II) carbonate碳酸銅 (II)

CuCO3

Cu = 63.5 C = 12.0 O = 16.0

Magnesium hydroxide氫氧化鎂

Mg(OH)2

Mg = 24.3 O = 16.0 H = 1.0

Calcium phosphate磷酸鈣

Ca3(PO4)2

Ca = 40.1 P = 31.0 O = 16.0

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2 The table below lists some information of two elements X and Y: 下表列出兩種元素 X和 Y的一些資料：

Element元素



X 7 14.0

Y 12 24.3

a) Assume elements X and Y can form an ionic compound. Deduce the chemical formula of this compound. 假設元素 X和 Y化合時會生成離子化合物，推斷該化合物的化學式。

b) Calculate the formula mass of the compound formed between X and Y. 計算由 X和 Y生成的化合物的式量。


72

共價鍵 c b

分子 m

鍵合電子對 b p e

雙原子分子 d m

分子式 m f

孤電子對 l p e

單鍵 s b

雙鍵 d b

三鍵 t b

給體原子 d a

受體原子 a a

配位共價鍵 d c b

相對分子質量 r m m

式量 f m

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1 A is formed when one or more pairs of outermost shell

electrons are shared between two atoms.

2 A covalent bond is the strong electrostatic forces of attraction between the

and the two positively charged nuclei of the bonded atoms.

3 Atoms of non-metallic elements can join together to form groups called .

4 The table below shows the electron diagrams and models of molecules of some common non-

metals.

Molecule Electron diagram Ball-and-stick model

Hydrogen

hydrogen molecule (H — H)

H H

H H

ChlorineCl Cl

chlorine molecule (Cl — Cl)

Cl Cl

Oxygen

O O



74


Nitrogen

N N

5 Atoms of different elements share electrons with each other to

form covalent compounds.

6 The table below shows the electron diagrams and models of molecules of some common covalent

compounds.


Hydrogen chlorineH Cl

Tetrachlormethan

Cl C

Cl

Cl

Cl


75



Water

H O H

AmmoniaH N

H

H

Carbon dioxideO C O

7 a) When a metal combines with a non-metal, an compound forms.

b) When non-metals combine, a compound forms.

8 A covalent bond is a covalent bond in which the bond pair electrons are

provided by the same atom.

9 In substances containing polyatomic ions, the cations and anions are held together by

bonding, but each polyatomic anion is a group of atoms held together by

bonding.

10 of an element or compound = sum of relative

atomic masses of all atoms present in one molecule of the element or compound

11 of an ionic compound = sum of the relative atomic masses of

all atoms making up one formula unit of the compound


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第 9節物質的性質與結構和化學鍵類別的關係

9.1 考慮一些物質的結構

物質的結構就是物質內粒子的排列方式。物質的性質取決於其結構。

Unit 9 Relating the properties of substances to structures and bonding (P.126)

9.1 A look at the structures of some substances (P.126)

The structure of a substance is the way in which its particles are arranged. The properties of a substance depend on its structure.

Table 9.1 The melting points and electrical conductivities of four common solids四種常見固體的熔點和導電性

Name名稱

Melting point熔點


Common salt食鹽

high高

good conductor in molten state or aqueous solution在熔融狀態或溶於水時是良好導電體

Quartz石英

high高

non-conductor非導電體

Sugar糖

low低


Copper銅

high高

conductor導電體

9.2 Giant ionic structure (P.127)

Ionic compounds such as sodium chloride consist of oppositely charged ions packed closely together in a regular pattern. Strong ionic bonds between oppositely charged ions hold the ions together.

Sodium chloride is made up of sodium ions and chloride ions packed in a regular pattern. This is called a lattice.

9.2 巨型離子結構

離子化合物（例如氯化鈉）包含帶相反電荷的離子，它們以有規律的方式緊密地擠在一起。強大的離子鍵把帶相反電荷的離子連結在一起。

氯化鈉由以有規律的方式擠在一起的鈉離子和氯離子組成，這個稱為晶格。

Fig. 9.1 Structure of sodium chloride 氯化鈉的結構

Cl–

Na+

Na+

Na+

Na+Cl–

Cl–

Cl–

Cl–

Cl–

Cl–Cl–

Cl–

Cl–

Cl–Cl–

Cl–

Cl–

Cl–

77

Unit 9 Relating the properties of substances to structures and bonding 物質的性質與結構和化學鍵類別的關係

9.3 Properties of ionic compounds (P.128)

(1) Hardness

Ionic compounds like sodium chloride are hard. This is due to the strong ionic bonds between oppositely charged ions. Relative motion of the ions is restricted.

(2) Melting point and boiling point

To melt or boil an ionic compound, we must overcome the strong attractive forces (ionic bonds) between the ions. A lot of heat is needed to do so. Therefore ionic compounds have high melting and boiling points.

(3) Solubility

Many ionic compounds are soluble in water but insoluble in non-aqueous solvents.

When we put sodium chloride into water, attractive forces exist between ions in sodium chloride and water molecules. These forces cause the sodium ions and chloride ions to move away from the solid and go into the water.

9.3 離子化合物的性質

(1) 硬度

離子化合物（例如氯化鈉）十分堅硬，這是因為帶相反電荷的離子之間的強大離子鍵，離子之間相對的移動受到限制。

(2) 熔點和沸點

要熔化或煮沸離子化合物，我們必須勝過離子之間強大的引力（離子鍵），這需要大量的熱。因此，離子化合物具有高的熔點和沸點。

(3) 溶解度

大部分的離子化合物均溶於水，但不溶於非水溶劑。

當我們把氯化鈉放進水，氯化鈉中的離子與水分子之間存在引力，這些引力令鈉離子和氯離子離開氯化鈉固體，進入水中。

Fig. 9.2 Sodium chloride is soluble in water 氯化鈉可溶於水

Cl– ion氯離子

Na+ ion鈉離子

water molecules水分子

Na+ ion鈉離子

Cl– ion氯離子

There are no such attractive forces between ions in sodium chloride and molecules of non-aqueous solvents. Hence sodium chloride is insoluble in non-aqueous solvents.

氯化鈉中的離子和非水溶劑的分子之間沒有這種引力，因此，氯化鈉不溶於非水溶劑。


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(4) Electrical conductivity

For any substance to conduct electricity, there must be charged particles which are free to move.

Ionic compounds conduct electricity in molten state or aqueous solution. They do not conduct electricity in solid state. In solid state, ions in the compound are held together by strong ionic bonds. They are not free to move. However, the ions become mobile in molten state or aqueous solution.

9.4 Giant covalent structures (P.130)

In substances with giant covalent structures, millions or more atoms are held together by strong covalent bonds.

The structure of diamond

Diamond is a form of carbon. In diamond, each carbon atom is surrounded by four other carbon atoms in the form of a tetrahedron. Hence the giant structure consists of a network of covalent bonds.

(4) 導電性

物質要導電一定要含有帶有電荷而可以自由流動的粒子。

離子化合物在熔融狀態或溶於水時可以導電，它們不能在固態時導電。在固態時，化合物中的離子藉着強大的離子鍵連結在一起，不能自由流動。可是，在熔融狀態或溶於水時，離子則變成可以流動。

9.4 巨型共價結構

在具有巨型共價結構的物質中，百萬個或以上的原子藉着強大的共價鍵連結在一起。

鑽石的結構

鑽石是一種形式的碳。在鑽石中，每個碳原子被四個碳原子以四面體形的方式包圍，所以這個巨型結構是由網狀的共價鍵組成的。

Fig. 9.3 Part of the structure of diamond 鑽石的結構的一部分

carbon atom碳原子

key:索引：

79


The structure of graphite

Graphite is another form of carbon. It differs from diamond only in the arrangement of atoms. Graphite and diamond are allotropes.

石墨的結構

石墨是另一種形式的碳。它與鑽石的分別只在於其原子的排列方式，石墨和鑽石是同素異形體。

Allotropes are two (or more) forms of the same element in which the atoms or molecules are arranged in different ways.

同素異形體是同一個元素的兩種（或以上）的形式，其中的原子或分子以不同的方式排列。

In graphite, the carbon atoms are arranged in flat parallel layers.

在石墨中，碳原子以平而且平行的原子層的方式排列。

Fig. 9.4 The structure of graphite 石墨的結構

van der Waals’ forces范德華力

key:索引：

carbon atom碳原子

Within each layer, each carbon atom is covalently bonded to three other atoms, forming a hexagonal arrangement. We can consider each layer to be a two-dimensional network of carbon atoms.

Each carbon atom has four outermost shell electrons. Each carbon atom in graphite uses three electrons in forming covalent bonds. The remaining electron is delocalized between the layers of carbon atoms. The presence of delocalized electrons results in graphite being an excellent electrical conductor.

There are weak van der Waals’ forces between the adjacent layers in graphite. The layers can easily slide over each other. Hence graphite is soft and has a slippery feel.

在每層中，每個碳原子都會與三個碳原子以共價鍵鍵合，以六方形的方式排列。我們可將每層碳原子視為一個由碳原子組成的二維網狀結構。

每個碳原子具有四個最外層電子，每個碳原子只用了三個電子來形成共價鍵，剩下的電子可以在碳原子層之間流動，這些離域電子令石墨成為優良的導電體。

在石墨中，相鄰的碳原子層之間只有微弱的范德華力，這些原子層可以輕易地互相滑過。因此，石墨柔軟，而且具滑膩的觸感。


80

The structure of quartz

Quartz is a crystalline form of silicon dioxide.

In a quartz crystal, each silicon atom is joined to four oxygen atoms by covalent bonds, while each oxygen atom is joined to two silicon atoms by covalent bonds. Hence the giant structure consists of a network of covalent bonds. The overall ratio of silicon to oxygen is 1 : 2. Hence the chemical formula of silicon dioxide is SiO2.

石英的結構

石英是一種結晶形式的二氧化硅。

在石英晶體中，每個硅原子與四個氧原子藉着共價鍵連結，而每個氧原子則與兩個硅原子藉着共價鍵連結，因此，這個巨型結構是由網狀的共價鍵組成的。硅原子與氧原子的總比例是 1：2，所以二氧化硅的化學式是 SiO2。

Fig. 9.5 Part of the structure of quartz 石英結構的一部分

oxygen atom氧原子silicon atom硅原子

key:索引：

9.5 Properties of substances with giant covalent structures (P.132)

(1) Hardness

Substances with giant covalent structures consist of a network of covalent bonds. Relative motion of the atoms is restricted. This makes such substances very hard (except graphite). Diamond is the hardest substance known and is used in cutting tools.

(2) Melting point

To melt a substance with a giant covalent structure, we must overcome the strong covalent bonds between the atoms. A lot of heat is needed to do so. Hence these substances have high melting points.

(3) Solubility

Substances with giant covalent structures are insoluble in water and non-aqueous solvents. This is because the atoms are held together by strong covalent bonds and it is very diffi cult to separate the atoms.

9.5 具巨型共價結構的物質的性質

(1) 硬度

具巨型共價結構的物質包含網狀的共價鍵，原子之間相對的移動受到限制，令這類物質非常堅硬（石墨除外）。鑽石是已知最堅硬的物質，可用於切割工具。

(2) 熔點

要熔化具巨型共價結構的物質，我們必須勝過原子之間強大的共價鍵，需要大量的熱，因此，這類物質具有高熔點。

(3) 溶解度

具巨型共價結構的物質不溶於水及非水溶劑，這是因為原子之間藉着強大的共價鍵連結在一起，要分開這些原子十分困難。

81



In substances with giant covalent structures, covalent bonds hold all the outermost shell electrons of the atoms fi rmly together. There are no mobile electrons or ions. Hence these substances do not conduct electricity (except graphite).

(4) 導電性

在具巨型共價結構的物質中，共價鍵把原子的所有最外層電子穩穩地連結，沒有可以流動的電子或離子。因此，這類物質不能導電（石墨除外）。

Table 9.2 Some properties of quartz, diamond and graphite石英、鑽石和石墨的一些性質

Substance物質

State at room temperature and

pressure在常温常壓下的狀態

Hardness硬度

Melting point(ºC)

熔點（ºC）

Solubilityin water在水中的溶解度


Quartz石英

solid 固態

very hard很高

1 610insoluble不溶於水


Diamond鑽石

solid 固態

very hard很高

3 500insoluble 不溶於水

non-conductor 非導電體

Graphite石墨

solid 固態

soft低

3 730insoluble不溶於水

conductor導電體

9.6 Applications of graphite (P.132)

Graphite is widely used because of its unique combination of properties. Graphite has a slippery feel. It is a good conductor of electricity and heat. It is also chemically inert and can withstand high temperatures and corrosive environments.

9.7 Simple molecular structures (P.134)

Some non-metals and compounds of non-metals such as iodine and dry ice consist of separate molecules. In these substances, strong covalent bonds hold the atoms in each molecule together. Much weaker van der Waals’ forces hold the separate molecules together.

The structure of iodine

In the structure of iodine (I2), the iodine molecules are packed close to one another in a regular pattern. Weak van der Waals’ forces hold the molecules together. The pattern is repeated millions of times, and the result is a crystal.

9.6 石墨的應用

石墨的用途廣泛，是因為它的性質的獨特組合。它具滑膩的觸感，是良好的導電體和導熱體，具化學惰性，能抵受高温和腐蝕性的環境。

9.7 簡單分子結構

一些非金屬或由非金屬的化合物，例如碘和乾冰，由分子組成。在這些物質中，強大的共價鍵把每個分子中的原子連結在一起。微弱的范德華力把個別分子連繫在一起。

碘的結構

在碘（ I2）的結構中，碘分子以有規律的方式擠在一起，微弱的范德華力把分子連繫在一起。這種排列方式會重複百萬次，結果是一個晶體。


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Fig. 9.6 The arrangement of iodine molecules in its crystal 碘分子在晶體中的排列方式

iodine molecule碘分子

key:索引：

The structure of dry ice

Dry ice consists of separate carbon dioxide (CO2) molecules. In each molecule, strong covalent bonds hold the carbon and oxygen atoms together. The carbon dioxide molecules are packed close to one another in a regular pattern. Weak van der Waals’ forces hold the molecules together.

9.8 Properties of substances with simple molecular structures (P.135)

(1) Hardness

Solid substances with simple molecular structures are usually soft because the attractive forces between the molecules are weak.

(2) Melting point and boiling point

The attractive forces between the molecules are weak. Little heat is needed to separate the molecules. Therefore substances with simple molecular structures have low melting and boiling points.

(3) Solubility

Substances with simple molecular structures are usually slightly soluble or insoluble in water but very soluble in non-aqueous solvents.

乾冰的結構

乾冰由個別的二氧化碳（CO2）分子組成。在每個二氧化碳分子中，強大的共價鍵把碳原子和氧原子連結在一起。二氧化碳分子以有規律的方式擠在一起。微弱的范德華力把分子連繫在一起。

9.8 具簡單分子結構的物質的性質

(1) 硬度

具簡單分子結構的固態物質一般都柔軟，因為分子之間的引力微弱。

(2) 熔點和沸點

分子之間的引力微弱，只需少許的熱便可把分子分開，因此，具簡單分子結構的物質具有低熔點和沸點。

(3) 溶解度

具簡單分子結構的物質一般都微溶或不溶於水，卻非常溶於非水溶劑。

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Take iodine as an example. It is slightly soluble in water but very soluble in non-aqueous solvents. The attractive forces between water molecules are quite strong. The weak attractive forces between iodine and water molecules are not strong enough to overcome the attractive forces between the water molecules. Hence iodine molecules and water molecules do not mix easily.

以碘為例，它微溶於水，但非常易溶於非水溶劑。水分子之間的引力頗強，而碘分子和水分子之間的引力沒有水分子之間的引力那麼強。因此，碘分子和水分子不易混合在一起。

Fig. 9.7 Iodine is slightly soluble in water 碘微溶於水

Fig. 9.8 Iodine is very soluble in non-aqueous solvents 碘非常易溶於非水溶劑

weak attractive forces between iodine and

water molecules碘分子與水分子之間的引力微弱

attractive forces between water molecules are quite strong

水分子與水分子之間的引力頗強

iodine molecules碘分子

water molecules水分子

iodine molecules碘分子

molecules of non-aqueous solvent非水溶劑分子

attractive forces between iodine molecules and molecules of non-aqueous solvent similar to those between molecules of non-aqueous solvent碘分子與非水溶劑分子之間的引力與非水溶劑分子之間的引力相若

On the other hand, the attractive forces between molecules of non-aqueous solvents are similar to those between iodine molecules. The attractive forces between the two types of molecules are also similar to those between molecules of non-aqueous solvents. Hence iodine molecules and molecules of non-aqueous solvents mix together easily.

另一方面，非水溶劑分子之間的引力與碘分子之間的引力相若，兩種分子之間的引力與非水溶劑分子之間的引力亦相若。因此，碘分子與非水溶劑分子容易混合在一起。


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Fig. 9.9 The giant structure of magnesium 鎂的巨型結構

magnesium ion鎂離子electron電子

key:索引：

mobile electrons流動的電子


Substances with simple molecular structures do not conduct electricity because they do not contain mobile electrons or ions.

9.9 Giant metallic structures (P.137)

In a metal, ions are packed tightly together in a regular pattern to form a giant structure. This type of giant structure is called a giant metallic structure.

(4) 導電性

具簡單分子結構的物質不導電，因為它們不含可以流動的電子或離子。

9.9 巨型金屬結構

在金屬內，離子以有規律的方式緊密地擠在一起，形成巨型結構，這類結構稱為巨型金屬結構。

9.10 Properties of metals (P.137)

(1) Density

Metals generally have high densities due to the close packing of their ions.

(2) Melting point

The ions in metals are packed closely and the metallic bonds holding them together are very strong. To melt a piece of metal, a lot of heat is needed to overcome the strong attractive forces. Hence metals generally have high melting points.

9.10 金屬的性質

(1) 密度

金屬一般具有高密度，因為離子的緊密排列。

(2) 熔點

金屬中的離子緊密地擠在一起，而且連結它們在一起的金屬鍵十分強。要熔化一片金屬，需要大量的熱才能勝過這樣強大的引力，因此，金屬一般具有高熔點。

Table 9.3 The densities and melting points of some common metals一些常見金屬的密度及熔點

Metal金屬

Density ( g cm–3)密度（g cm–3）


Copper 銅 8.9 1 083

Gold 金 19.3 1 063

Iron 鐵 7.9 1 538

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(3) Electrical and heat conductivity

Metals are good conductors of electricity due to the movement of mobile electrons in a metal. When a metal is connected to a battery, mobile electrons in the metal fl ow towards the positive terminal of the battery. At the same time, electrons fl ow into the other end of the metal from the negative terminal of the battery.

Metals are also good conductors of heat. When heating one end of a piece of metal, the mobile electrons get more energy. They move faster and collide with neighbouring electrons. This helps to transfer the heat.

(4) Malleability and ductility

Metals are both malleable and ductile. Metals can be hammered or rolled into thin sheets as they are malleable. Ductile metals can be drawn into wires.

Ions in metals are packed in layers. When we apply a force to a piece of metal, the layers slide through the ‘sea’ of electrons to new positions. The metal does not break because the ions are still bound together by the ‘sea’ of electrons. As a result, metals can be hammered into thin sheets or pulled into long, thin wires.

(3) 導電及導熱性

金屬是良好的導電體，因為金屬內流動的電子的移動。金屬片被連接至電池時，金屬片內的流動電子會流向電池的正端鈕。與此同時，電子會從電池的負端鈕流入金屬片的另一端。

金屬亦是優良的導熱體。把金屬片的一端加熱，流動的電子會獲得較多能量。它們移動得更快，並會與相鄰的電子互撞，這樣有助把熱傳遞。

(4) 延展性

金屬是可展和可延的。金屬可被錘擊或捲成薄片，因為它們是可展的。可延的金屬可被拉成線狀。

金屬內的離子一層層地排列。當我們對金屬施力時，各層會滑過「電子海」至新的位置。金屬不會斷裂因為離子仍被「電子海」連結在一起。結果金屬可被錘擊成薄片，或被拉成線狀。

force applied here在這兒施力

Fig. 9.10 When a force is applied to a piece of metal, the ion layers slide through the ‘sea’ of electrons to new positions without breaking the metallic bond

於一片金屬施力時，各金屬離子層就會在「電子海」中滑動至新的位置，但金屬鍵卻不受影響


86

1 Both carbon and silicon are Group IV elements. The diagram below shows the structures of dry ice (solid carbon dioxide) and quartz (silicon dioxide).

碳和硅都是第 IV族元素。下圖顯示乾冰（固態二氧化碳）和石英（二氧化硅）的結構。

key:索引：

oxygen atom氧原子silicon atom硅原子

key:索引：

carbon dioxide molecule二氧化碳分子

dry ice乾冰

quartz石英

a) With reference to the structures of the two substances, explain why quartz is a solid while carbon dioxide is a gas at room conditions.

參照這兩種物質的結構，解釋為甚麼在室温下，石英是固體而二氧化碳是氣體。

b) With reference to its structure, explain why silicon dioxide can be used as an abrasive. 為甚麼二氧化硅適合作為磨蝕劑？根據它的結構加以解釋。

2 The table below shows the electrical conductivities of three substances in the solid state. 下表列出三種物質在固態時的導電性。

Lead鉛

Bromine溴

Lead(II) bromide溴化鉛 (II)

Electrical conductivity in solid state固態時的導電性

conducting可以導電

non-conducting不能導電

non-conducting不能導電

a) Explain the difference in electrical conductivity between lead and lead(II) bromide in the solid state. 解釋鉛和溴化鉛 (II)在固態時的導電性的差異。

b) Will lead(II) bromide conduct electricity in the molten state? Explain your answer. 溴化鉛 (II)在熔融狀態時能否導電？試解釋之。

3 Consider the following two compounds: 細閱以下化合物：

potassium chloride and hydrogen chloride 氯化鉀、氯化氫

State, with explanation, which of the two compounds has a higher melting point. 以上哪一種化合物的熔點較高？試解釋之。

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9.11 Predicting properties of substances from their structures (P.141)

From the group numbers of elements that make up a compound, we can tell the type of bonding present and the structure of the compound. We can then predict the properties of the compound from its structure.

9.11 從物質的結構預測其性質

從化合物的成分元素的族數，我們可以推斷該化合物是離子化合物還是共價化合物，以及其結構。從化合物的結構，我們可以推斷它的性質。

1 A compound Z is formed from the reaction between elements X and Y. Electronic arrangements of atoms of the two elements are given below.

化合物 Z是由兩種元素（X和 Y）化合而成的。下表展示元素 X和 Y的原子的電子排佈。

Element元素


X 2,8,8,1

Y 2,8,7

a) Predict the type of bonding present in Z. 推斷存在於 Z的化學鍵種類。

b) Draw an electron diagram of Z (showing electrons in the outermost shells only). 繪出 Z的電子圖（只需顯示最外層的電子）。

c) What type of structure does Z have? Z的結構屬哪一類別？

d) Predict and explain the following properties of Z: 推斷及解釋 Z的一些性質：

i) melting point and boiling point; and 熔點和沸點；及

ii) electrical conductivity. 導電性。

2 Silicon carbide (SiC) has a structure similar to that of diamond. 碳化硅（SiC）的結構和鑽石的相似。

a) Draw the three-dimensional structure of silicon carbide. 繪出碳化硅的三維結構。


88

b) Predict and explain the following properties of silicon carbide: 推斷及解釋碳化硅的一些性質：

i) hardness; 硬度；

ii) melting point. 熔點。

9.12 Predicting structures of substances from their properties (P.145)

The properties of a substance can help us to predict its structure. Information about the state (at room temperature and pressure), melting point and electrical conductivity of a substance is very useful when predicting its structure.

9.12 從物質的性質預測其結構

物質的性質可以幫助我們預測其結構。預測物質的結構時，它在常温常壓下的狀態、熔點和導電性等資料都十分有用。

no否

no否

no否

no否

Property of substance物質的性質

Structure of substance物質的結構

yes是

yes是

yes是

yes是

yes是

simple molecular structure簡單分子結構

giant metallic structure巨型金屬結構

giant ionic structure巨型離子結構

giant covalent structure巨型共價結構

Is the substance a liquid or a gas at room temperature and pressure?在常温常壓下是液體或氣體嗎？

Does it conduct electricity in molten state or aqueous solution?

在熔融狀態或溶於水時能否導電？

Does the solid melt easily?固體是否容易熔化成液體？

Does it conduct electricity in solid state?在固態時能否導電？

Does it have a very high melting point?熔點是否很高？

Fig. 9.11 Predicting the structure of a substance from its properties 利用物質的性質推斷它們的結構

89


1 Classify the structure of each of the following substances as either giant ionic, giant covalent, simple molecular, or giant metallic.

下列每個物質的結構屬哪一類別：巨型離子結構、巨型共價結構、簡單分子結構還是巨型金屬結構？

a) A yellow solid that melts at 105 °C to form a clear yellow liquid. Both the solid and liquid forms do not conduct electricity.

一黃色固體在 105 ºC熔化，形成澄清的黃色液體。它在固態和液態時都不能導電。

b) A solid that melts at 99 °C to form a silvery liquid. Both the solid and liquid forms are good conductors of electricity.

一固體在 99 ºC熔化，形成銀白色液體。它在固態和液態時都是良好導電體。

c) A dark shiny solid that melts at 114 °C. It is a poor conductor of electricity and heat. 一有光澤的黑色固體在 114 ºC熔化。它是不良的導電體和導熱體。

d) A white solid that melts at 872 °C to form a colourless liquid. The solid form does not conduct electricity while the liquid form conducts electricity.

一白色固體在 872 ºC熔化，形成無色液體。它在固態時不能導電，液態時則能導電。

e) A solid that melts at 3 600 °C. Both the solid and liquid forms do not conduct electricity. 一固體在 3 600 ºC熔化。它在固態和液態時都不能導電。

2 Boron trifluoride (BF3) and aluminium fluoride (AlF3) differ markedly in their melting points. 三氟化硼（BF3）和氟化鋁（AlF3）的熔點差異很大。

Compound化合物


BF3 –144

AlF3 1 290

a) Deduce the type of bonding present in each compound. 推斷存在於上述化合物中的化學鍵的類別。

b) Draw an electron diagram to show the bonding present in each compound (showing electrons in the outermost shells only).

利用電子圖顯示存在於上述化合物中的化學鍵（只需顯示最外層的電子）。


90

3 Consider the melting points and boiling points of four substances at 1 atmospheric pressure. 考慮以下四種物質在 1個大氣壓強下的熔點和沸點：

Substance物質



Bromine溴

–7 59

Silane (SiH4)硅烷（SiH4）

–185 –112

Neon氖

–248 –246

Sulphur dioxide二氧化硫

–75 –10

a) Which substance exists as a liquid at –50 °C and 1 atmospheric pressure? Explain your choice. 在 –50 °C和 1個大氣壓強下，哪種物質以液態存在？試解釋之。

b) Name one type of attractive forces that exists in all the four substances at 25 °C and 1 atmospheric pressure.

說出在 25 °C和 1個大氣壓強下，以上四種物質都具有的引力。

Aluminium — a versatile metalAluminium is the world’s most abundant metal, and the third most abundant element overall, after oxygen and silicon. It makes up about 8% by mass of the Earth’s crust.

Properties of aluminium

Applications of aluminium reflect its properties, in particular its low density, corrosion resistance and electrical conductivity

Strength to mass ratio

Aluminium has a density about one third that of steel. It is used in applications where high strength and low mass are required.

鋁 — 多功能的金屬鋁是地殼中蘊藏量最高的金屬，也是豐度第三高的元素，僅次於氧及硅。鋁約佔地殼總質量的 8%。

鋁的特性

從鋁的用途亦可窺看到它的性質，尤其是它低密度、抗腐蝕及導電的特性。

強度質量比

鋁的密度只及鋼的三分之一。因此，如果需要一種強度高而質輕的金屬，鋁便能滿足這個要求。

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Corrosion resistance

When the surface of aluminium is exposed to air, an oxide layer forms almost instantaneously. This oxide layer protects the metal beneath from further attack.

Electrical and heat conductivities

Aluminium is an excellent conductor of both electricity and heat.

Toxicity

Aluminium is non-poisonous. In addition to that, it does not release any odours or taint products with which it is in contact.

Applications of aluminium

Packaging

Aluminium is probably the most versatile packaging material available today.

Aluminium foil is totally opaque to ultraviolet light, which can quickly cause deterioration of many foods. It is also impervious to gases and water vapour. Aluminium foil is also strong, non-poisonous and shows good heat and cold resistance. Thus, aluminium foil is used in many applications, such as pharmaceutical and food packaging.

抗腐蝕性

鋁曝露於空氣中時，一層氧化物會在其表面瞬間生成。這層氧化物可保護金屬免受進一步的腐蝕。

導電性和導熱性

鋁是優良的導電體和導熱體。

毒性

鋁不具毒性。此外，與食物接觸時，它既不會產生難聞的氣味，也不會污染食物。

鋁的用途

包裝

現時，鋁可能是世界上最多功能的包裝物料。

鋁箔能完全阻隔可令食物迅速變壞的紫外光，也能阻隔空氣和水。除此之外，鋁箔亦具高強度、無毒性、不受温度影響等優點。因此，鋁箔十分適合用來包裝食物及藥物。

Fig. 9.12 Aluminium is widely used in food packaging 鋁被廣泛應用於食物包裝

Heavier foil containers are used for convenience foods and take-away meals.

The aluminium beverage can is popular because it is light, unbreakable and the most recyclable package.

以較厚的鋁箔製成的容器可用來盛載便利食品及外賣食物。

鋁罐質輕，亦不會像玻璃般容易碎裂。與其他製造飲料罐的物料比較，它也十分易於循環再做。因此，鋁被廣泛用來製造飲料罐。


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Transport

The high strength and low density of aluminium makes it the prime material for the construction of aircraft. Low mass results in reduced fuel consumption.

Various aluminium alloys are also used in the construction of trains, ships, buses and bicycles.

交通工具

製造重量較低的飛機有助節省燃油開支。鋁的高強度和低密度的性質令它成為製造飛機的首選物料。

鋁合金也可用來製造火車、輪船、巴士及自行車。

Fig. 9.13 Aluminium and its alloys are used in the construction of (a) aircraft (b) monorail 用鋁及鋁合金製造的 (a) 飛機 (b) 單軌列車

(a) (b) Fig. 9.14 Aluminium used in buildings

在大廈中使用的鋁材

Building and architecture

The lightness of structures made of aluminium makes them much easier to handle. It also costs less to support these structures. Its self-protecting oxide layer means that aluminium needs no further treatment against oxygen in the air.

Aluminium used in buildings covers a wide range of applications, such as window frames, roofing, shop fronts and architectural hardware.

Questions

1 Aluminium is used to make overhead power transmission lines. List properties of aluminium that make it suitable for this application.

2 Tin-plated steel has been used to make food cans since the invention of canned food. Aluminium is now being used to make cans too.

Suggest ONE advantage and ONE disadvantage of using aluminium to make food cans.

建築工程

鋁的密度低。鋁製的建築組件，不單較易於搬運，用於承托組件的費用也較低。鋁表面生成的氧化層也使它能抵抗被進一步氧化，因此，無須額外為鋁材加上保護層。

鋁在建築方面的用途十分廣泛。它可用來製造窗框、蓋屋頂的物料、店鋪的櫃檯及建築用的金屬配件。

問題

1 一般都會用鋁來製造架空電纜。試舉出一些鋁的性質，令它適合作此用途。

2 自發明罐裝食物以來，盛載食物的罐子都是由外層鍍了一層錫的馬口鐵製成。現時，生產商亦會用鋁來製造這些罐子。

舉出用鋁來製造盛載食物的罐子的一項優點和一項缺點。

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晶格 l

同素異形體 a

范德華力 v d W f

可展的 m

可延的 d


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1 The following table summarizes the properties of substances with the four types of structures:

giant ionic, giant covalent, simple molecular and giant metallic.

Type of structure

Giant ionic Giant covalent Simple molecular Giant metallic

Where this type of structure is found

compounds formed between

and

Group

elements and some of their compounds

some

elements and some compounds formed between

Examplessodium chloride, magnesium oxide

diamond, graphite, silicon dioxide

hydrogen, iodine, ammonia, dry ice

aluminium, copper, magnesium

Particles present

ions atoms small moleculespositive ions surrounded by a ‘sea’ of electrons

example:NaCl

example:diamond

example:dry ice

example: magnesium

Bonding

ionic bonds

atoms joined by

covalent bonds

covalent bonds within the molecules;

van der Waals’ forces hold separate molecules together

metallic bonds


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Type of structure

Giant ionic Giant covalent Simple molecular Giant metallic

Common state(s) at room temperature and pressure

,

or

Hardness but

very

(in case of three-dimensional network structure)

solids usually

,

and

Melting point and boiling point

Solubility in water and non-aqueous solvents

usually

in water but

in non-aqueous solvents

in water and non-aqueous solvents

usually

in water but

in non-aqueous solvents

usually

in water and non-aqueous solvents

Electrical conductivity

conductors when molten or in aqueous solution

(except graphite)

conductors

2 are two (or more) forms of the same element in which the atoms or molecules

are arranged in different ways.

3 From the group numbers of elements that make up a compound, we can tell the

of bonding present and the of the compound. We can then predict the

of the compound from its structure.

4 Information such as (at room temperature and pressure),

and of a substance can help

us to predict its structure.

Unit 5 Atomic structure (P.2)

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