According to molecular orbital theory, atomic orbitals of nearly same energy of different atoms are combined and form molecule. In homodiatomic molecule two atomic orbitals which have wave function psi_(A) and psi_(B) are combined in two ways (psi_(A)pm psi_(B)) . They have two type of electron density, one is bonding [(psi_(A) pm psi_(B))^(2)] where e- density increase between nucleus. Another is antibonding [(psi_(A)pm psi_(B))^(2)] where e^(-) density decreases between nucleus. These molecular orbitals are filled according to Hund, Pauli, afbau principle. Existence of molecule depends on bond order. where bond order = ("Number of bonding "e^(-)"s- number of antibonding "e^(-)s)/(2) lf the molecule have unpaired electron it is paramagnetic otherwise diamagnetic Statement- 1: Removal of two e^(-) from N^(2), magnetic behaviour does not change while addition of two electrons in O_(2) magnetic behaviour changes. Statement-2: In N_(2) removal of electron talces place from bonding orbital while addition of e^(-)in O_(2) is in antibonding orbital