The difference between the radii of $3^{\mathrm{rd}}$ and $4^{\mathrm{th}}$ orbits of $\mathrm{Li^{2+}}$ is $\Delta R_1$. The difference between the radii of $3^{\mathrm{rd}}$ and $4^{\mathrm{th}}$ orbits of $\mathrm{He^+}$ is $\Delta R_2$. Ratio $\Delta R_1 : \Delta R_2$ is :

JEE Main 2020 · ChemistryMultiple choiceSingle correctMediumCalculation

JEE Main 5 September 2020, Shift 1, Chemistry Q41

Question 41 of 75 in this shift, Chemistry question 16 of 25.

The difference between the radii of

3^{\mathrm{rd}}

and

4^{\mathrm{th}}

orbits of

\mathrm{Li^{2+}}

\Delta R_1

. The difference between the radii of

3^{\mathrm{rd}}

and

4^{\mathrm{th}}

orbits of

\mathrm{He^+}

\Delta R_2

. Ratio

\Delta R_1 : \Delta R_2

is :

(1)3 : 8
(2)8 : 3
(3)3 : 2
(4)2 : 3Official answer

Official answer

Option 4

NTA final key (Sep 2020).

Chapter: Structure of Atom
Topic: Bohr's Atomic Theory
Idea tested: Bohr Radius Calculation

Same idea in other shifts

Asked 8× in all

4 Apr 2026, Shift 2 · Q52The species having identical radii according to the Bohr's theory are: A. H (first orbit) B. $\mathrm{He^+}$ (first orbit) C.…EasyOther
6 Apr 2026, Shift 2 · Q52The Bohr radius of a hydrogen like species is 70.53 pm. The species and the stationary state ( $n$ ) are respectively (Given : Hydrogen atom…EasySingle correct
2 Apr 2025, Shift 1 · Q52According to Bohr's model of hydrogen atom, which of the following statement is incorrect ?EasySingle correct
26 Jun 2022, Shift 1 · Q63If the radius of the 3 $^{rd}$ Bohr's orbit of hydrogen atom is r $_3$ and the radius of 4 $^{th}$ Bohr's orbit is r $_4$ . Then :EasySingle correct
3 Aug 2021, Shift 2 · Q53The ratio of radii for the first and third orbits of hydrogen atom is $1 : x$ . The value of $x$ is $\underline{\hspace{2em}}$ . (Integer…EasyNumerical value
8 Jan 2020, Shift 2 · Q29The radius of the second Bohr orbit, in terms of the Bohr radius, $\mathrm{a_0}$ , in $\mathrm{Li^{2+}}$ is :EasySingle correct
2 Apr 2017 (offline) · Q38The radius of the second Bohr orbit for hydrogen atom is : (Planck's Const. $h=6.6262\times10^{-34}$ Js; mass of electron…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.