Chemistry - PERIODIC TABLE Question with Solution | TestHub

In general the ionic radius increases on moving from top to bottom in group and decreases on moving from left to right in period. So, Na⁺> Li⁺and Mg²⁺> Be²⁺.

The size of Mg²⁺is however smaller than Li⁺. Despite the Mg atom having a slightly larger atomic size, the Mg²⁺ion is marginally smaller in size than the Li⁺ion because of its higher nuclear charge

Hence, the correct trend is

$\text{N}{\text{a}}_{0.98\text{Å}}^{+}>\text{L}{\text{i}}_{0.68\text{Å}}^{+}>\text{M}{\text{g}}_{0.65\text{Å}}^{2+}>\text{B}{\text{e}}_{0.62\text{Å}}^{2+}$