JEE Main Chemistry question

Na^+, Mg^{2+}, Al^{3+}, Si^{4+} are isoelectronic. Their ionic size follows the order

(A)Na^+ < Mg^{2+} < Al^{3+} < Si^{4+}
(B)Na^+ > Mg^{2+} < Al^{3+} < Si^{4+}
(C)Na^+ < Mg^{2+} > Al^{3+} > Si^{4+}
(D)Na^+ > Mg^{2+} > Al^{3+} > Si^{4+}Correct

Answer: (D)

Solution

All four ions have the same number of electrons (isoelectronic, neon-like with 10 electrons), but their nuclear charge increases in the order Na(11) < Mg(12) < Al(13) < Si(14). For isoelectronic species,

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Question ID VK-133386