Covalent bonding

Covalency is the sharing of electrons between the atoms of non-metals. A covalent bond is formed when two atoms of non-metal contribute electron(s) equivalent to their valencyValency or Valence of an element is a measure of an atom's ability to combine with other atoms to create molecules or chemical compounds. More for sharing.

After the bonding, both atoms will attain a stable octet or duplet structure of rare gases. Electrons are not transferred because the atoms involved are electron acceptors. The pair of electrons shared is known as the shared pair of electrons.

Diatomic molecules are formed by covalent bonding. e.g. Cl₂, H₂, N₂, O₂. In Chlorine molecules, only one electron is used in forming a covalent bond. The other six electrons form three lone pairs of electrons.

Formation of Chlorine molecule (Cl₂):

Formation of Hydrogen molecule (H₂):

Formation of Oxygen molecule (O₂):

Formation of Nitrogen Molecule (N₂):

Formation of Water Molecule (H₂O):

A water molecule contains 2 lone pairs of electrons and two shared pairs of electrons. The water molecule is a V-shape.

The mode of formation of H₂S is similar to that of H₂O.

Formation of Ammonia (NH₃):

Ammonia molecule contains 1 Lone pair of electrons and 3 shared pairs of electrons.

Ammonia molecule is pyramidal-shaped. The mode of formation of PH₃, PCl₃, and NCl₃ is similar to that of HN₃.

Formation of Methane (CH₄):

Methane molecule (CH₄) contains 4 shared pairs of electrons. CH₄ molecule is tetrahedral in shape. The mode of formation and the shape of CCl₄ are similar to that of CH₄.

 Formation of Carbon (IV) Oxide (CO₂):

Carbon (IV) oxide molecule – CO₂

 CO₂ is Linear shape O = C = O

Types of Covalent Bonds:

1. Non-polar covalent bond.

2. Polar covalent bond.

1. Non-Polar Covalent Bond:

Non-polar covalent bonds are covalent bonds formed between two non-metals of the same or about the same electronegativity. In non-polar molecules, electron pair is shared equally i.e. there is a uniform distribution of electron densityDensity is the measurement of how tightly a material is packed together i.e. how closely the particles are packed in the material. The tighter the material is packed the more its... More around the nuclei. e.g N₂, H₂, Cl₂ ,Br₂

2. Polar Covalent Bond:

Polar covalent bonds are covalent bonds formed between two non-metals having different electronegativity. The electron pair is not shared equally i.e non-symmetrical. The atoms carry partial separation of charges called permanent dipole e.g H₂O, HCl, H₂S, HF

Factors that Determine Covalent Bonds:

1. Electronegativity.

2. Electron affinity.

3. Ionization EnergyEnergy is the ability to do work. Energy exists in several forms such as heat, kinetic or mechanical energy, light, potential energy, and electrical energy. Units of Energy: The SI unit... More.

Characteristic Properties of Covalent Compounds:

1. They have low melting and boiling points.

2. They are non-electrolytes or they do not conduct electricity.

3. They are not soluble in water or polar solvents, but soluble in non-polar solvents like Benzene, ether, etc.

4. They are gases or volatile liquidsA liquid that evaporates readily at normal temperature is known as a volatile liquid. Volatile liquids are liquids that transform easily into the vapour phase. Usually, the vapour pressure of volatile... More.

5. They consist of molecules.