Give reasons:

(a) Covalent compounds have low melting point.

(b) For covalent bond formation both atoms should have high ionisation.

(c) Covalent bond formation takes place when both atoms should have four or more electron in outermost shell.

(a) Covalent compounds have low melting and boiling points because they have weak forces of attraction between the binding molecules, thus less energy is required to break the force of bonding.

(b) When both atoms have high ionisation, the energy required to remove electrons from them is very large. Thus, transfer of electrons is not possible. The atoms share electrons to complete their octet. Hence they form covalent bonds.

(c) The atoms that have four or more electrons in outermost shell do not favour the loss of their electrons due to energy considerations and thus transfer of electrons is not possible. So, they form covalent bonds to achieve stable electronic configuration.