CHAPTER NUMBER EIGHT (8)

CHEMICAL REACTIVITY

Prepared By:

MUHAMMAD XAMEER RAJA

INTRODUCTION

• Chemical reactivity refers to the ease with which a chemical compound tends to react when it comes into contact with other compounds. An element or a compound will be said to have high reactivity if it reacts fast when it interact with another substance. Such a compound may also be viewed as having high reactivity in terms of how many substances it can react with. Some of the common substances used to determine the chemical reactivity of elements include water, hydrochloric acid, sulphuric acid, chlorine gas, pure oxygen, air and many others

FACTORS ON WHICH CHEMICAL REACTIVITY DEPEND

• Reactivity can be influenced by several internal and external factors. Some of these factors are as follow

• 1) Temperature, • 2) Pressure, • 3) Surface area, • 4) Amount of the substance and • 5) Catalysts.

REASONS FOR CHEMICAL REACTION• A chemical reaction is

purely related to chemistry whether it is happening between material or human bodies.

• The reaction happens in all the three stages solids, liquids and gases. All chemical reaction is based on electrons. It means electrons are the main cause and the main difference in the processes are named as combination reaction and displacement reaction.

CLASSIFICATION OF ELEMENTS ON THE BASIS OF REACTIVITY:

• Metals and Nonmetals:The majority of the chemical elements in pure form are classified as metals.

• An Element may be either metal or nonmetal.

• There physical as well as chemical properties are as follow.

CHEMICAL PROPERTIES

• Metals

• Usually have 1-3 electrons in their outer shell.

• Lose their valence electrons easily.

• Form oxides that are basic.

• Are good reducing agents.

• Have lower electronegativities

• Non Metals

• Usually have 4-8 electrons in their outer shell.

• Gain or share valence electrons easily.

• Form oxides that are acidic.

• Are good oxidizing agents.

• Have higher electronegativities

PHYSICAL PROPERTIES

• Metals• Good electrical conductors and heat conductors.

• Malleable - can be beaten into thin sheets.

• Ductile - can be stretched into wire.

• Possess metallic luster.• Opaque as thin sheet.• Solid at room temperature (except Hg).

• Non Metals• Poor conductors of heat and electricity.

• Brittle - if a solid.

• Nonductile.• Do not possess metallic luster.

• Transparent as a thin sheet.

• Solids, liquids or gases at room temperature

Periodic Table Of Elements Showing Metals And Non Metals:

SOME OF THE IMPORTANT METALS: 1) GOLD (Au)

2) IRON (Fe)

3) COPPER(Cu)

SOME OF THE REACTIONS OF METALS AND NON METALS:

» 1. When two elements react, a combination reaction occurs producing a binary compound (that is, one consisting of only two types of atoms).

• If a metal and a nonmetal react, the product is ionic with a formula determined by the charges on the ions the elements form.

• If two nonmetals react, the product is a molecule with polar covalent bonds, with a formula consistent with the normal valences of the atoms involved. Some pairs of elements may react only slowly and require heating for significant reaction to occur.

• Examples:

• Ca + O2 --------> CaO (ionic)• Al + I2 ---------> AlI3 (ionic)• H2 + O2 ---------> H2O (covalent)

REACTION OF METAL AND NON METAL OXIDES WITH WATER:

Reaction of a metal oxide with water produces a metal hydroxide; that is, a strong base. Reaction of a nonmetal oxide with water produces an oxyacid in which the nonmetal is in the same oxidation state as in the oxide you started with.

• Examples:• Na2O + H2O -----> NaOH BASIC• MgO + H2O ------> Mg(OH)2 BASIC• SO2 + H2O ------> H2SO3 ACIDIC

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