Question

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

• A. $Al^{3+} > Mg^{2+} > Na^{+} > F^{-} > O^{2-}$
• B. $Na^{+} > Mg^{2+} > Al^{3+} > O^{2-} > F^{-}$
• C. $Na^{+} > F^{-} > Mg^{2+} > O^{2-} > Al^{3+}$
• D. $O^{2-} > F^{-} > Na^{+} > Mg^{2+} > Al^{3+}$

Answer 1

Answer: (D)

$O^{2-} > F^{-} > Na^{+} > Mg^{2+} > Al^{3+}$

Answer 2

For isoelectronic species higher the $\frac{Z}{e}$ ratio , smaller the ionic radius $\frac{Z}{e}$ for $O^{2-} = \frac{8}{10} = 0.8$ $F^{-} = \frac{9}{10} = 0.9$ $Na^{+} = \frac{11}{10} = 1.1$ $Mg^{2+} = \frac{12}{10} = 1.2$ $Al^{3+} = \frac{13}{10} = 1.3$