Question

In an isoelectronic species, the ionic radii (A) of $N^{3-},O^{2-}$ and $F^{-}$ are respectively given by:

• A. $1.36,1.40,1.71$
• B. $1.36,1.71,1.40$
• C. $1.71,1.40,1.36$
• D. $1.71,1.36,140$

Answer 1

Answer: (C)

$1.71,1.40,1.36$

$N^{3-}$,$O^{2-}$ and $F^{-}$ all have 10 electrons each. Thus they are iso electronic . For iso electronic species atomic size is inversely proportional to effective nuclear charge . Effective nuclear charge is inversely proportional to negative charge . $N^{3-}$ has maximum negative charge maximum atomic size . Similarly size of $O^{2-}$>$F^{-}$.