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Choose the Best Answer · Q19

Q.Which of the following orders of ionic radii is correct?

(a) H⁻ > H⁺ > H
(b) Na⁺ > F⁻ > O²⁻
(c) F > O²⁻ > Na⁺
(d) None of these
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Step 1. Check (a): H- (2 electrons, largest), H (neutral, 1 electron), H+ (a bare proton, essentially zero radius, smallest). The true order is H−>H>H+H^- > H > H^+, not H−>H+>HH^- > H^+ > H as (a) states -- (a) is wrong.

Step 2. Check (b): Na+, F-, O2- are isoelectronic (10 electrons each, Ne configuration). Radius grows as charge becomes more negative, so the true order is O2−>F−>Na+O^{2-} > F^- > Na^+, exactly the reverse of the Na+>F−>O2−Na^+ > F^- > O^{2-} that (b) states -- (b) is wrong. …

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