Covalent bonds - Chemistry

Covalent Bonds

Covalent Bond

Covalent Bond

Covalent Bond

Covalent Bond

Covalent BondCovalent Bond

Covalent BondCovalent Bond

Covalent Bond

• Bond that is usually formed between by• Non-metal such as hydrogen , carbon and oxygen

do not lose electron from their outer shell .• They do not form positive ions by losing electrons .

However their outer shells are incomplete. • Electron need to be added to the outer shells to

attain the stability of the noble gas atoms.• When the atoms of two non-metals react , all the

atom need to gain electrons to complete the octet shell of electrons. They can do this by sharing electrons between them .

sharing of electronnon-metal atoms

Lewis Structure

• Shows how the valence electrons of the atoms are arranged in the molecules .

• Example

a ) A helium atom has two valence electron *click to see

He ..

b ) A neon atom has eight valence electrons

Ne ::. .

. .

• Rules for Writing Lewis Structuresi ) Add up the valence electrons of all the atom in the molecule. Example : CO2

: C : O O = 16 valence electrons

ii ) Use a pair of electrons to form a bond between each pair of atomsiii ) Arrange it like this

x x o o

x x

o o

x x o o

O : C : O

xxxx

xx

oo oo

oo

Another example : Hydrogen

H HXO

HH O x

OxygenO2

ChlorineCl2

IodineI2

NitrogenN2

Phosphorus

P4

SulphurS8

Other molecules the are held together by covalent bond

Single Bond

Chlorine Molecule

ClCl

Cl Cl

Cl Cl

Cl Cl

Cl Cloctet

Cl Cloctet

Cl ClThe octet is achieved byeach atom sharing theelectron pair in the middle

Cl ClThe octet is achieved byeach atom sharing theelectron pair in the middle

Cl ClThis is the bonding pair

Cl ClIt is a single bonding pair

Cl ClIt is called a SINGLE BOND

Double bond can also be shown as single dash

Cl - Cl

Water• H2O

Methane• CH4

Tetrachloromethane• CCL4

Ammonia• NH3

Another example of Single Bond

Double Bond

sometimes simple is better -_-

Oxygen

How will two oxygen atoms bond?

OO

OOEach atom has two unpaired electrons

OO

OO

OO

OO

OO

OO

Oxygen atoms are highly electronegative.

So both atoms want to gain two electrons.

OO

Oxygen atoms are highly electronegative.

So both atoms want to gain two electrons.

OO

OO

OO

OO

OO

OOBoth electron pairs are shared.

6 valence electronsplus 2 shared electrons

= full octet

OO

6 valence electronsplus 2 shared electrons

= full octet

OO

two bonding pairs,

OOmaking a double bond

Double bond can also be shown as double dashes

O = O

Carbon Dioxide•CO2