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Topic Isoelectronic species
Asked 2 times across 2 UPSC exams over 1 years (2021–2022), peaking in 2021.
Key insights
- Most tested in NDA — 1 of 2 PYQs
- Most asked in 2021
- Recurs across 2 years (2021–2022)
How it travelled across exams
First appearance in each exam — the same idea, reframed.
NDA 2021 → GEO 2022
How the concept evolved
Rising — more than half its appearances (2 of 2) are since 2016.
Related concepts
Ideas UPSC tests alongside this one — keep exploring.
Sample questions
You've seen the pattern — here are a few of the actual PYQs.
GEO2022
A species that is not isoelectronic with 35/17 Cl- is
- A 31/15 P3-
- B 32/16 S2-
- C 40/18 Ar2+ ✓
- D 39/19 K+
✓ Correct answer: (C)
Science & Technology › Physics & Chemistry
NDA2021
Which one of the following ions is not iso-electronic with F– ?
- A O2–
- B Na+
- C Ne
- D N– ✓
✓ Correct answer: (D)
Science & Technology › Physics & Chemistry
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