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NEET CHEMISTRYEasy

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

1

O2−,F−O^{2-}, F^-

2

Na+,Mg2+Na^+, Mg^{2+}

3

Mn2+,Fe3+Mn^{2+}, Fe^{3+}

4

Fe2+,Mn2+Fe^{2+}, Mn^{2+}

Step-by-Step Solution

Isoelectronic species have the same number of electrons. Fe2+Fe^{2+} has 26−2=2426-2=24 electrons, while Mn2+Mn^{2+} has 25−2=2325-2=23 electrons. Thus, they are not isoelectronic.

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