Question

The correct sequence which depicts a decreasing order of ionic radii of the given elements is:

• A. $A{l}^{3+}$ > $M{g}^{2+}$ >$N{a}^{+}$ >$F^{-}$> $O_2^{-}$
• B. $O_2^{-}$ > $F^{-}$ >$N{a}^{+}$ >$M{g}^{2+}$ > $A{l}^{3+}$
• C. $C{a}^{2+}$ > $K^{+}$ >$C{l}^{-}$ > $S^{2-}$ > $P^{3-}$
• D. $P^{3-}$> $S^{2-}$ > $C{l}^{-}$ > $K^{+}$ > $C{a}^{2+}$

Answer 1

Answer: (B), (D)

The correct options are
B $O_2^{-}$ > $F^{-}$ >$N{a}^{+}$ >$M{g}^{2+}$ > $A{l}^{3+}$
D $P^{3-}$> $S^{2-}$ > $C{l}^{-}$ > $K^{+}$ > $C{a}^{2+}$

All the species given in the options are isoelectronic containing 10 $e^{-}$ each. For isoelectronic species, as the number of protons increases size decreases.