Question

Which one of the following pair of elements has similar properties?

• A. 10, 12
• B. 11, 20
• C. 21, 33
• D. 13, 31

Answer 1

Answer: (D)

The elements $13$ (Aluminium) and $31$ (Galium) both belong to same group i.e., III A. Therefore, both elements have similar electronic configuration of the outermost shell and hence have similar properties.
$Al\left(1s^{2}2s^{2}2p^{6}3s^{2}3p^1\right)$
$Ga\left(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{10}4s^{2}4p^1\right)$