Consider the following electronic configuration 

this configuration violates

Aufbau's principle is not violated;

(1)In ‘1s’ orbital both electrons have same spin;

This violates Pauli's principle;

(2)In ‘2p’ subshell all the three unpaired electrons in degenerate orbitals must have parallel spin to have maximum exchange energy. This is Hund's rule. But one of the unpaired electron has opposite spin. This violates Hund's rule.