Question

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

• 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

The correct option is C

1.71, 1.40 and 1.36

Number of electrons in $N^{3-},=7+3=10$
Number of electrons in $O^{2-}=8+2=10$
Number of electrons in $F^{-}=9+1=10$

Since all the three species have 10 electrons each, hence they are isoelectronic species.
It is considered that, in case of isoelectronic species as the negative charge increases, ionic radii increases and therefore the value of ionic radii are
$N^{3-}=1.71$ (highest among the three)
$O^{2-}=1.40$
$F^{-}=1.36$ (lowest among the three)