Question

The following is the correct increasing order of the ionic radii

• A. $Li^{+} < Mg^{2+} < K^{+} < Al^{3+}$
• B. $Al^{3+} < Li^{+} < Mg^{2+} < K^{+}$
• C. $Al^{3+} < Mg^{2+} < K^{+} < Li^{+}$
• D. $K^{+} < Al^{3+} < Mg^{2+} < Li^{+}$

Answer 1

Answer: (B)

$L i^{+}=60\, pm,\, K^{+}=133\, pm,\, Mg^{2+}=65\, pm$,
$A l^{3+}=53.5\, pm$
The correct increasing order of ionic radii is
$Al^{3+} < Li^{+} < Mg^{2+} < K^{+}$
In general, on moving from left to right, the ionic radii decreases due to increased effective nuclear charge.
On moving down a group, the number of shells increases and that why ionic radii increase.