Question

Identify the correct order in which the ionic radius of the following ions increases:
(I) $F^{-}$
(II) $N{a}^{+}$
(III) $N{a}^{3-}$

• A. III, I, II
• B. I, II, III
• C. II, III, I
• D. II, I, III

Answer 1

Answer: (D)

The species (atoms or ions) having the same number of electrons are known as isoelectronic species. In iso-electronic species, the size increases with the increase of negative charge and decrease of positive charge.
$($ size $\propto \frac{1}{z/e\text{ratio}}).$ i.e. effective nuclear charge.
Decreasing order of size.
$C^{4-}>N^{3-}>O^{2-}>F^{-}>Ne>N{a}^{+}>M{g}^{2+}>A{l}^{3+}>S{i}^{4+}$