A -1s2 , 2s2 , 2p6 , 3s2 , 3p3 (group -15 period – 3)
B – 1s2 , 2s2 , 2p4 (group –16 period – 2)
C – 1s2 , 2s2 , 2p6 , 31 (group – 1 period – 3)
D – 1s2 , 2s2 , 2p6 , 3s2 , 3p6 (group – 18 period – 3)
E – 1s2 , 2s2 , 2p6 , 3s2 , 3p6 , 4s2 .(group – 2 period – 4)
F – 1s2 , 2s2, 2p6 , 3s2 , 3p6 , 3d10 , 4s2 , 4p4 (group – 16 period – 4)
G – 1s2 , 2s2 , 2p6 (group – 18 period – 2)
a. A, D same period ;
B, G same period 1
b. B, F same group ;
D, G same group