Question

The ionic radii (in $\mathring{A}$) of $N^{3-}$, $O^{2-}$ and $F^{-}$ are respectively :

• A. $1.36,1.40$ and $1.71$
• B. $1.36,1.71$ and $1.40$
• C. $1.71,1.40$ and $1.36$
• D. $1.71,1.36$ and $1.40$

Answer 1

Answer: (C)

$1.71,1.40$ and $1.36$

The ionic radii (in $\mathring{A}$) of $N^{3-}$, $O^{2-}$ and $F^{-}$ are respectively $1.71,1.40$ and $1.36$.

$N^{3-}$, $O^{2-}$ and $F^{-}$ contains ten electrons each. Hence, they are isoelectronic species.

For isoelectronic species, the nuclear charge increases on moving from left to right in a period.

This decreases the ionic radii as the valence electrons are more strongly attracted by the nucleus.