FORMATION OF

COMPOUNDS

� Atom of noble gas achieved the stable electron

arrangement (duplet or octet).

� They do no need to donate, accept or sharing

electron with other atoms. Thus cannot react with

other atoms.

Electron arrangement of

neon : 2.8 (octet)

Electron arrangement

of Helium : 2 (duplet)

� The Atoms are not achieved the stable electron

arrangement (duplet or octet) .

� Atom should donate, accept or share electron with

other atoms to achieved stable electron

arrangement and react to form ionic or covalent

compound.

Why atom of others

elements are not stable?

Why inert gases are

stable?

CHEMICAL BONDS IONIC BONDS COVALENTL BONDS

Formed by transfer of

electrons from metal atom to

non-metal

Metal

(Group 1,2,13)

Negative ions

(anion)

Attracted by strong

electrostatic force Positive ions

(cation)

Conduct electricity

in molten

High melting and

boiling points

Covalent compounds

Non-metal atoms share electron to achieve stable octet

electron arrangement

Not conduct

electricity

Non metal

(Group 15,16,17)

Ionic compounds

Formed by sharing of electrons between non-metals

Low melting points

Formed through Formed through

Donate electron Accept electron Pull together by

Weak Van Der Waals forces

Draw the diagram of the formation of sodium chloride, NaCl

� Atom Magnesium has 2 valence electron and atom Cl has 7

valence electron

� Electron arrangement of magnesium atom is 2.8.2

� Magnesium atom donate two electron to two atom chlorine

form magnesium ion, Mg2+ and achieve a stable octet electron

arrangement.

� Electron arrangement of Chlorine atom is 2.8.7

� Each chlorine atom accept one electron from magnesium atom

to form chloride ion, Cl- and achieve the stable octet electron

arrangement.

� The magnesium ion, Mg2+ and chloride ion, Cl- are attracted to

each other with strong attraction force to form ionic

compound, Magnesium chloride MgCl2

+ -

2+ - -

Mg Mg2+ + 2e

Cl + e Cl-

Sodium ion, Na+ and chloride ion, Cl- are attracted to each

other with strong attraction force to form sodium chloride

compound, NaCl

Accept one electron Donate one electron

Atom

(Neutral) Positive ion (cation) Negative ions (anion)

Donate electron

Charge of 11 protons = +11

Charge of 11 electrons = -11

Total charge = 0

Charge of 11 protons = +11

Charge of 10 electrons = -10

Total charge = +1

2.8.1 2.8

to achieve the stable

octet electron

arrangement

NaCl

Electron arrangement 2.8.1 2.8.7

Na Cl

2.8 2.8

Charge of 17 protons = +17

Charge of 18 electrons = -18

Total charge = -1

Charge of 17 protons = +17

Charge of 17 electrons = -17

Total charge = 0

2.8.7 2.8.8

accept electron

+ -

Formation of Sodium Chloride Formation of Magnesium Chloride

Donate electron accept electron

Sodium ions , Na+ Sodium atom, Na Chlorine atom, Cl Chlorine atom, Cl-