. The ions O2 minus F minus

O2-,F-,Na+,Mg2+ and Al3+ are isoelectronic. Their ionic radii show

(a) a significant increase from O2- to Al3+

(b) a significant decrease from O2- to Al3+

(c) an increase from O2- to F- and then decrease from Na+ to Al3+

(d) a decrease from O2- to F- and then increase from Na+ to Al3+.

Best Answer

Correct Option is: B

Among isoelectronic species, the ion with the largest positive charge is the smallest when different numbers of electrons can be removed to form ions with varying charges. When one or more electrons are added to a neutral atom, electron–electron repulsions rise and the effective nuclear charge decreases, causing the atom's size to expand and vice versa for cation. Among isoelectronic ions, ionic radii of anions are more than that of cations.

Remember this trend in isoelectronic species : Anion > Parent atom > Cation


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