Question

Which of the following is the correct order of increasing size?

• A. $C{l}^{-}<C{a}^{2+}<S^{2–}<A{l}^{3+}$
• B. $M{g}^{2+}<K^{+}<L{i}^{+}<A{l}^{3+}$
• C. $M{g}^{2+}<N{a}^{+}<F^{-}<O^{2–}<N^{3–}$
• D. $F^{-}<N{a}^{+}<M{g}^{2+}<O^{2–}$

Answer 1

The correct option is C $M{g}^{2+}<N{a}^{+}<F^{-}<O^{2–}<N^{3–}$

In isoelectronic species , size is inversely related to the atomic number. And also,
+ve charge $\uparrow$ Atomic size $\downarrow$
-ve charge $\uparrow$ Atomic size $\uparrow$
So, an isoelectronic species with the highest negative charge and least atomic number will have the largest size.
Option C is correct