Question

Four elements P, Q, R and S have ground state electronic configuration as:
$P\to 1s^{2}2s^{2}2p^{6}3s^{2}3p^{3}Q\to 1s^{2}2s^{2}2p^{6}3s^{2}3p^{1}R\to 1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{10}4s^{2}4p^{3}S\to 1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{10}4s^{2}4p^1$
Select the correct statement (s) among the following:

• A. Size of $Q$ < size of $S$ (appreciable difference)
• B. Size of $R$ < size of $S$
• C. Size of $P$ < size of $Q$
• D. Size of $P$ < size of $R$ (appreciable difference)

Answer 1

Answer: (B), (C), (D)

Size of $P$ < size of $R$ (appreciable difference)

P - Phosphorus (P), R - Arsenic (As)
Q - Aluminium (Al), S- Gallium (Ga)
As we know, according to the general trend, on going left to right in a period of the periodic table, size decreases and on moving top to bottom in a group, size increases.
But due to the poor screening effect of $3d$ electrons, the size of $Ga$ is less than that of $Al$
(A) $P<Al$
(B) $As<Ga$
(C) $P<As$
(D) $Al>Ga$