Question

The ionic radius of $N{a}^{+}$ ion is 1.02 Å. The ionic radii (in Å) of $M{g}^{2+}$ and $A{l}^{3+}$, respectively are:

• A. 0.72 and 0.54
• B. 0.68 and 0.72
• C. 1.05 and 0.99
• D. 0.85 and 0.99

Answer 1

The correct option is A 0.72 and 0.54

Answer: (a)
$N{a}^{+},M{g}^{2+}andA{l}^{3+}$ are isoelectronic species.

For iso-electronic system,
$r\propto \frac{1}{Z_{effective}}$
So, ionic radius decrease on increasing atomic number for isoelectronic species.
Hence, from the options we can say option (a) is the correct answer.
$N{a}^{+}-1.02\stackrel{\circ }{A}M{g}^{2+}-0.72\stackrel{\circ }{A}A{l}^{3+}-0.54\stackrel{\circ }{A}$