Question

An atom has electronic configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 3d³ 4s², you will place it in 

(a) fifth

(b) fifteenth

(c) second

(d) third

Answer 1

Correct option (a) fifth

Explanation :

The electronic configuration of an atom 

1s² 2s¹ 2p⁶ 3s² 3p⁶ 3d³ 4s². 

In the configuration, the last electron of the atom is filled in d sub-shell as 3d³. Thus this element belongs to d-block of the periodic table with group no. V.