JEE Main 2025 · PhysicsMultiple choiceSingle correctEasyCalculation

JEE Main 2 April 2025, Shift 2, Physics Q40

Question 40 of 75 in this shift, Physics question 15 of 25, Section A.

Assuming the validity of Bohr's atomic model for hydrogen like ions the radius of

\mathrm{Li^{++}}

ion in its ground state is given by

\frac{1}{X}a_0

, where

X =

__________. (Where

a_0

is the first Bohr's radius.)

(1) $1$
(2) $2$
(3) $3$ Official answer
(4) $9$

Official answer

Option 3

NTA final key.

Chapter: Atoms
Topic: Bohr's Atomic Model
Idea tested: Bohr Orbit Radius

Same idea in other shifts

Asked 6× in all

27 Jan 2024, Shift 1 · Q47The radius of third stationary orbit of electron for Bohr's atom is R. The radius of fourth stationary orbit will be :EasySingle correct
6 Apr 2023, Shift 1 · Q53The radius of fifth orbit of the $\mathrm{Li^{++}}$ is ____________ $\times10^{-12}$ m. Take: radius of hydrogen atom = 0.51 ÅEasyNumerical value
6 Apr 2023, Shift 2 · Q56Experimentally it is found that 12.8 eV energy is required to separate a hydrogen atom into a proton and an electron. So the orbital…MediumNumerical value
13 Apr 2023, Shift 1 · Q51The radius of $2^{\text{nd}}$ orbit of $\mathrm{He^+}$ of Bohr's model is $r_1$ and that of fourth orbit of $\mathrm{Be^{3+}}$ is…EasyNumerical value
30 Jul 2022, Shift 2 · Q17Using Boh'r model of quantization of angular momentum the relation between the radius 'r' of the n $^{\mathrm{th}}$ allowed orbit of…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.