Question

The pair of atomic numbers belonging to the same group are:

• A. 11, 20
• B. 12, 30
• C. 13, 31
• D. 14, 33

Answer 1

The correct option is C 13, 31

$Z=13\left[Ne\right]3s^{2}3p^1$
$Z=31\left[Ar\right]3d^{10}4s^{2}4p^1$
As valence electronic configuration is same, they belong to same group.