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Chemistry Question on Molecular Orbital Theory

The ions N3−,O2−,F−,Na+Mg2+{{N}^{3-}},{{O}^{2-}},{{F}^{-}},N{{a}^{+}}M{{g}^{2+}} are isoelectronic. Their ionic radii show

A

an increase from N3−{{N}^{3-}} to F−{{F}^{-}} and then decrease from Na+N{{a}^{+}} to Mg2+M{{g}^{2+}}

B

a decrease from N3−{{N}^{3-}} to F−{{F}^{-}} and then increase from Na+N{{a}^{+}} to Mg2+M{{g}^{2+}}

C

a significant increase from N3−{{N}^{3-}} to Mg2+M{{g}^{2+}}

D

a significant decrease from N3−{{N}^{3-}} to Mg2+M{{g}^{2+}}

Answer

a significant decrease from N3−{{N}^{3-}} to Mg2+M{{g}^{2+}}

Explanation

Solution

Ionic radii
∝1effective nuclear charg⁡e(Zeff)\propto \frac{1}{effective\text{ }nuclear\text{ }ch\arg e({{Z}_{eff}})}
∝negative charge\propto negative\text{ }charge
∝1positive charge\propto \frac{1}{positive\text{ }charge}
Hence, as the negative charge increases, ionic radii increases and with increase in positive charge ionic radii decrease. Hence, ionic radii decreases from
N3−{{N}^{3-}} to Mg2+M{{g}^{2+}}