Question

The correct sequence which shows decreasing order of the ionic radii of the elements is :

• A. $A{l}^{3+}>M{g}^{2+}>N{a}^{+}>F^{-}>O^{2-}$
• B. $N{a}^{+}>M{g}^{2+}>A{l}^{3+}>O^{2-}>F^{-}$
• C. $N{a}^{+}>F^{-}>M{g}^{2+}>O^{2-}>A{l}^{3+}$
• D. $O^{2-}>F^{-}>N{a}^{+}>M{g}^{2+}>A{l}^{3+}$

Answer 1

The correct option is D $O^{2-}>F^{-}>N{a}^{+}>M{g}^{2+}>A{l}^{3+}$

All the given species contains $10e^{-}$ each i.e. isoelectronic.
For isoelectronic species, anion having high negative charge is the largest in size and cation having high positive charge is the smallest in size.
So, the correct order is :
$O^{2-}>F^{-}>N{a}^{+}>M{g}^{2+}>A{l}^{3+}$