State and explain Hund's rule of maximum multiplicity by taking an example of nitrogen.

Explanation

Hund.s rule states that in the orbitals of same subshell electron pairing will not take place till each orbital is singly filled. Also, all these singły filled orbitals should have electrons with parallel spin. If we take an example of nitrogen which has three valence electrons to be filled in 2p orbitals, then we have three possible ways of filling 2p orbitals.
Third (III) type of arrangement is correct while remaining two are wrong. Electrons are negatively charged species. At first, they will be filled in orbitals one by one. In this way, there is minimum repulsion between electrons. Atom in minimum energy state will possess maximum stability.