1) O2−,F− Both have 10 electrons
2) Na+,Mg+2 Both have 10 electrons
3) Mn2+,Fe+3 Both have 23 electrons
4) Mn2+ has 23 electrons while, Fe+2 have 24 electrons so, they are not an iso-electronic pair.
NEET UG 2021 — Chemistry Physical Chemistry
From the following pairs of ions which one is not an iso-electronic pair?
Held on 30 Apr 2021 · Verified 9 Jul 2026.
O2−,F−
Na+,Mg+2
Mn2+,Fe3+
Fe2+,Mn2+
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