JEE Main · 2022 · 27 Jun 2022 · Shift 2 · Classification of Elements and Periodicity

The correct order of increasing ionic radii is

(A) $Mg^{2 +} < Na^{+} < F^{-} < O^{2 -} < N^{3 -}$ ✓ Correct
(B) $N^{3 -} < O^{2 -} < F^{-} < Na^{+} < Mg^{2 +}$
(C) $F^{-} < Na^{+} < O^{2 -} < Mg^{2 +} < N^{3 -}$
(D) $Na^{+} < F^{-} < Mg^{2 +} < O^{2 -} < N^{3 -}$

Answer: (A)

Solution

All five species are isoelectronic (10 electrons each). For isoelectronic species, ionic radius decreases with increasing nuclear charge. The nuclear charges are:

N^{3 -}

(7),

O^{2 -}

(8),

F^{-}

(9),

Na^{+}

(11),

Mg^{2 +}

(12). Therefore, the order of increasing ionic radii is

Mg^{2 +} < Na^{+} < F^{-} < O^{2 -} < N^{3 -}

JEE Main · 2022 · 27 Jun 2022 · Shift 2 · Single correct option

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