1. O²⁻, F^- 2. Na^+, Mg²⁺ 3. Mn²⁺, Fe³⁺ 4. Fe²⁺, Mn²⁺

Answer: 4. Fe²⁺, Mn²⁺ Key idea: iso-electronic species have the same number of electrons. mathrmO²⁻ (10) and F^- (10): yes Na^+ (10) and mathrmMg²⁺ (10): yes mathrmMn²⁺ (23) and mathrmFe³⁺ (23): yes mathrmFe²⁺ (24) and mathrmMn²⁺ (23): no So option 4 is not an iso-electronic pair.

Topic: Atomic and ionic radii· Classification of Elements and Periodicity in Properties

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

1. \(O^{2-}, F^-\)

2. \(Na^+, Mg^{2+}\)

3. \(Mn^{2+}, Fe^{3+}\)

4. \(Fe^{2+}, Mn^{2+}\)

Doubtly Asked 30 Oct 2026 NEET UG 2021 Practice test neet Save WhatsApp Report

1 answer

Best answer

Answer: 4. \(Fe^{2+}, Mn^{2+}\)

Key idea: iso-electronic species have the same number of electrons.

\(\mathrm{O^{2-}}\) (10) and \(\mathrm{F^-}\) (10): yes
\(\mathrm{Na^+}\) (10) and \(\mathrm{Mg^{2+}}\) (10): yes
\(\mathrm{Mn^{2+}}\) (23) and \(\mathrm{Fe^{3+}}\) (23): yes
\(\mathrm{Fe^{2+}}\) (24) and \(\mathrm{Mn^{2+}}\) (23): no

So option 4 is not an iso-electronic pair.

Doubtly AI · 30 Oct 2026 AI-generated · not yet verified Report

Was this answer helpful?

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

1 answer

Your answer