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Saturday, 31 October

JEE Main · Chemistry · Classification of Elements and Periodicity in Properties

Configurations of Isoelectronic Species

JEE Main asked Configurations of Isoelectronic Species 2 times in 2 of the 108 shifts Lumi analysed, in 2017 and 2022. It belongs to Quantum Numbers, in Classification of Elements and Periodicity in Properties (Chemistry). The longest wait between two years asking it was 5 years, across 2018 and 2019, which Lumi has no shifts for.

Updated 2026-10-24

Times asked
2
in 2 shifts
Years
2 of 8
First asked
2017
last in 2022
Pattern
Occasional
across the analysed shifts

Questions on this idea a shift, by year

2017–2026. Asked in 2017 and 2022. Years differ in how many shifts Lumi analysed, so each year is scaled to one shift of 25 Chemistry questions.

00.510.83’170’200’210.03’220’230’240’250’26

Raw count: 2017: 1 in 1 shift · 2020: 0 in 12 shifts · 2021: 0 in 24 shifts · 2022: 1 in 24 shifts · 2023: 0 in 12 shifts · 2024: 0 in 18 shifts · 2025: 0 in 8 shifts · 2026: 0 in 9 shifts.

Shift by shift

Each square is one analysed shift, in date order. Open a filled one for that paper.

  • 20260 of 9
  • 20250 of 8
  • 20240 of 18
  • 20230 of 12
  • 20221 of 24
  • 20210 of 24
  • 20200 of 12
  • 20171 of 1

Asked in that shift More than once Not asked

How JEE Main framed it

Single correct is the usual form. Skill tested: application.

  • Identify group of isoelectronic species
  • Identify non-isoelectronic pair of ions

Difficulty

Easy 1Medium 1Hard 0

Every question was multiple choice.

Every question

All 2 questions

From the official JEE Main shift papers, newest first. Open one for the full question, the options and the official answer.

  1. 28 Jul 2022, Shift 2 · Q38Which of the following pair is not isoelectronic species? (At. no. Sm, 62; Er, 68; Yb, 70; Lu, 71; Eu, 63; Tb, 65; Tm, 69)MediumSingle correct
  2. 2 Apr 2017 (offline) · Q45The group having isoelectronic species is :EasySingle correct

Shifts: 2 Apr 2017 (offline), 28 Jul 2022, Shift 2.

Same topic

Other ideas in Quantum Numbers

Quantum Numbers has 23 ideas JEE Main has asked; 9 of them came up in more than one question. The 12 most asked are below.

Topic analysisChapter analysisStudy this chapterAll repeated ideas