(I) n=4,I=2,mI=−2,s=−21; represents 4d(n+I=6) (II) n=3,I=2,ml=1,s=+21; represents 3d(n+I=5) (III) n=4,I=1,mI=0,s=+21; represents 4p(n+I=5) (IV) n=3,I=1,ml=−1,s=+21; 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+I ) Energy =(I)>(II)=( III )>(IV) Step-2 : If n↑, then energy increases Energy =(I)>( III )>( II )>( IV)