Q. The ions $O^{2 -},\ F^{-},Na^{+},Mg^{2 +}$ and $A1^{3 +}$ are isoelectronic. Their ionic radii show
A) A decrease from $O^{2 -}$ to $F^{-}$ and then increase from $Na^{+}to\ Al^{3 +}$
B) A significant increase from $O^{2 -}to\ Al^{3 +}$
C) A significant decrease from $O^{2 -}to\ Al^{3 +}$
D) An increase from $O^{2 -}to\ F^{-}$ and then decrease from $Na^{+}\ to\ Al^{3 +}$
Explanation
(c)
In case of isoelectronic species
Ionic radius $\propto \frac{1}{nuclear\ charge\ }$
Thus, the order of ionic radii of given ions is
$O^{2 -} > F^{-} > Na^{+} > Mg^{2 +} > Al^{3 +}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.