Saturday, 17 January 2015

5.3 Formation of Covalent Bonds

Covalent bonds
■ Covalent bonds

Chemical bond formed through the sharing of electrons between two non-metal atoms.

During the formation of covalent molecules, each non-metal atom provides one or more electrons to be shared with other atom.

Through the electron sharing, each non-metals will achieve duplet or octet electron arrangement.
■ Types of covalent bonds

The types of covalent bond formed depends on the number of pairs of electron shared between two atoms.

There are three types of covalent bond as shown in the table below.
Number of pairs of electron shared between two atoms Type of covalent bond Example of molecule
1 Single covalent bond Hydrogen molecule, H2 ( H - H )
2 Double covalent bond Oxygen molecule, O2 (O = O)
3 Triple covalent bond Nitrogen molecule, N2 (N ≡ N)
A covalent bond can be represented by a straight line between the atom.
Formation of single covalent bond
■ Single covalent bond

Sharing of a pair of electrons between two non-metal atoms.

Each non-metal atom contributes one electron for sharing to achieve a stable electron arrangement.

Example : hydrogen, H2; chlorine, Cl2; hydrogen chloride, HCl2; water, H2O; methane, CH4; ammonia, NH3; tetrachloromethane, CCl4
■ Formation of single covalent bond

The animation below shows the formation of single covalent bond.
■ This video contains information on the formation of single covalent bond.

Formation of double covalent bond
■ Double covalent bond

Sharing of two pair of electrons between two non-metal atoms.

Each non-metal atom contributes two electron for sharing to achieve a stable electron arrangement.

Example : oxygen, O2; carbon dioxide, CO2
■ Formation of double covalent bond

The animation below shows the formation of double covalent bond.
Formation of triple covalent bond
■ Triple covalent bond

Sharing of three pair of electrons between two non-metal atoms.

Each non-metal atom contributes three electron for sharing to achieve a stable electron arrangement.

Example : nitrogen, N2
■ Formation of triple covalent bond

The animation below shows the formation of triple covalent bond in nitrogen molecule, N2.
■ This video contains information on the formation of double and triple covalent bond.

Determining the formulae of covalent compound
■ Formulae of covalent compounds.

Covalent compounds comprise element from group 14, 15, 16, and 17. (non-metal).
■ Determining the formulae of covalent compounds.

A non-metal element M need x electrons to achieve stable electron arrangement.

A non-metal element N need y electrons to achieve stable electron arrangement.


Thus, the formula of the covalent compound formed will be MyNx

■ Number of electron to achieve stable electron arrangement

Group Number of electron needed to achieve stable electron arrangement
Group 14 4
Group 15 3
Group 16 2
Group 17 1
■ Predicting the formula of a covalent compound.

Determine the number of electron needed to achieve stable electron arrangement.

Cross over the numbers of electron needed to achieve stable electron arrangement.

The animation below shows the way of predicting the formula of covalent compound.


⇲ For exercise(objective and subjective), download for free on Android OS.

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