The basic cause of chemical bonding is to attain noble gas configuration either by transfer of electron from a metal to non-metal or by sharing of electrons between two non-metal atoms. All the atoms have a tendency to acquire stable state or noble gas configuration and is called Octet Rule.
Atoms of elements in a molecule are held together by Chemical Bonding. The formation of chemical bonds result in the lowering of energy which is less than the energy of the individual atoms. The resulting compound is lower in energy and hence more stable.
There are two types of chemical bonding:
Ionic Bonding: The chemical bond formed by transfer of electrons from a metal to a non-metal is known as Ionic Bond or Electrovalent bond. Ionic compounds are solid, hard, have high melting and boiling points. They are soluble in water but insoluble in organic solvents. They are good conductor of electricity in molten state and in aqueous solution.
Covalent Bonding: The chemical bond formed by mutual sharing of equal number of electrons between two atoms. On the basis of sharing of number of electrons by each atom, covalent compounds are classified as single bonded, double bonded and triple bonded.
When sharing of one electron takes place from both the atoms, single bond is formed. For example, Cl-Cl or Cl2 and H-H or H2. Double bond is formed when two similar atoms share two pair of electrons. For example, O=O or O2. Triple bond is formed when there is sharing of three electrons from each atom. For example, N≡N or N2.
Covalent compounds mostly have liquid or gaseous state. Some are solid also. They have low melting point, low boiling point. They are insoluble in water but soluble in organic compounds. They are non-conductor of electricity.