; represents 3p(n+I=4) Order of energy depends on the (n+I), greater is the (n+I) value greater is the energy, if (n+I) is same, then it depends on n; if ' n ' is more, energy is more. Step-1: According to (n+1) Energy =(I)>(II)=(III)>(IV) Step-2 : If n↑, then energy increases Energy =(I)>( III )>( II )>( IV )