JEE Main 2020 · ChemistryMultiple choiceSingle correctMediumRecall

JEE Main 9 January 2020, Shift 1, Chemistry Q36

Question 36 of 75 in this shift, Chemistry question 11 of 25, Section A.

The electronic configurations of bivalent europium and trivalent cerium are : (atomic number : Xe = 54, Ce = 58, Eu = 63)

(1) $[\mathrm{Xe}]\ 4f^{7}\ 6s^{2}$ and $[\mathrm{Xe}]\ 4f^{2}\ 6s^{2}$
(2) $[\mathrm{Xe}]\ 4f^{2}$ and $[\mathrm{Xe}]\ 4f^{7}$
(3) $[\mathrm{Xe}]\ 4f^{7}$ and $[\mathrm{Xe}]\ 4f^{1}$ Official answer
(4) $[\mathrm{Xe}]\ 4f^{4}$ and $[\mathrm{Xe}]\ 4f^{9}$

Official answer

Option 3

NTA final key (Jan 2020).

Chapter: The d- and f-Block Elements
Topic: f-Block Elements
Idea tested: Lanthanide Electronic Configuration

Same idea in other shifts

Asked 8× in all

4 Apr 2026, Shift 2 · Q59Pairs of elements with the same number of electrons in their respective 4f orbital are [Atomic number: Eu-63, Gd-64, Dy-66, Ho-67, Tm-69,…MediumOther
6 Apr 2024, Shift 1 · Q69The number of element from the following that do not belong to lanthanoids is Eu, Cm, Er, Tb, Yb and LuEasySingle correct
27 Jan 2024, Shift 1 · Q68The electronic configuration for Neodymium is : [Atomic Number for Neodymium 60]EasySingle correct
27 Jun 2022, Shift 2 · Q69The 'f' orbitals are half and completely filled, respectively in lanthanide ions [Given : Atomic no. Eu, 63; Sm, 62; Tm, 69; Tb, 65; Yb,…MediumSingle correct
4 Aug 2021, Shift 1 · Q40Match List I with List II List I List II A. Gadolinium (At. No. 64) I. $5f^7, 6d^1, 7s^2$ B. Holmium (At. No. 67) II. $5f^4, 6d^1, 7s^2$ …MediumMatch the list
25 Jul 2021, Shift 2 · Q58Number of electrons present in 4f orbital of $\mathrm{Ho^{3+}}$ ion is ________. (Given Atomic No. of Ho = 67)EasyNumerical value
5 Sep 2020, Shift 1 · Q37The correct electronic configuration and spin-only magnetic moment (BM) of $\mathrm{Gd^{3+}}$ ( $Z = 64$ ), respectively, are :EasySingle correct

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.