a. 1s^{2} , 2s^{2} , 2p^{6} , 3s^{2} , 3p^{6} , 3d^{7} , 4s^{2}

block – d; group – 9; period – 4.

b. 1s^{2} , 2s^{2} , 2p^{6} , 3s^{2} , 3p^{6} , 4s^{1}

block – s; group – 1; period – 4

C. 1s^{2} , 2s^{2} , 2p^{6} , 3s^{2} , 3p^{3}

block – p; group – 15; period – 3