Q47 / 200 · NEET 2021 · Chemistry

From the following pairs of ions which one is not an iso-electronic pair?

A
$O^{2 -}, F^{-}$
B
${Na}^{+}, {Mg}^{+ 2}$
C
${Mn}^{2 +}, {Fe}^{3 +}$
Correct answer
D
${Fe}^{2 +}, {Mn}^{2 +}$

Solution

1)

O^{2 -}, F^{-}

Both have

10

electrons

2)

{Na}^{+}, {Mg}^{+ 2}

Both have

10

electrons

3)

{Mn}^{2 +}, {Fe}^{+ 3}

Both have

23

electrons

4)

{Mn}^{2 +}

has

23

electrons while,

{Fe}^{+ 2}

have

24

electrons so, they are not an iso-electronic pair.

Hence, the correct answer is option: 'D'.

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