Define the following: (i) Bond order (ii) Hybridisation (iii) `sigma` -bond

Explanation

(i) Bond order: Bond order `= (N_(b)-N_(a))/(2)`
The number of bonds formed between the two bonded atoms in a molecule is called bond order.
(ii) Hybridisation: It is a process of mixing of atomic orbitals of the same atom with comparable energy to form equal number of new equivalent orbitals with same energy. The resultant orbitals are called hybridised orbitals and they possess maximum symmetry and definite orientation in space so as to minimise the force of repulsion between their electrons.
(iii) `sigma`- bond When two atomic orbitals overlap linearly along the axis, the resultant bond is called sigma `(sigma)` bond.