JEE Main · Chemistry · Structure of Atom

Bohr's Atomic Theory: JEE Main previous year questions

Name: Bohr's Atomic Theory: JEE Main previous year questions
Creator: Lumi

39 questions in the 108 JEE Main shifts Lumi analysed, in 8 of 8 years. Pattern: Asked most years. 15 came in 2024–26. Here is how it is asked and which ideas come back.

Questions: 39; in 39 of 108 shifts
Years asked: 8/8; last asked 2026
Chance in a shift: 47%; calibrated model, how we compute it
Weighted estimate: 0.4; model; history: 0.4 a shift on average, typically 0.2–0.7

Key findings

01
Asked in 8 of 8 years with analysed shifts and in 39 of 108 shifts: 39 questions, #84 of 196 topics. It came in every year with analysed shifts.
02
34% of its questions since 2020 tested an idea no earlier year had asked; 14 repeated an idea from the year before.
03
The most repeated idea is Bohr Radius Calculation, asked 8 times in 8 shifts (2017, 2020, 2021, 2022, 2025, 2026), most often as “ratio of bohr orbit radii”.
04
JEE Main has asked 14 of the 42 ideas in this topic; 24 have never been asked, directly or inside another question.
05
Mostly asked as numerical value (46%); 46% need a numerical answer, 56% are easy and 3% hard.
06
The skill tested most is calculation (72%), then conceptual (13%).

Questions a shift, year by year

Out of the 25 Chemistry questions in a shift. Years differ in how many shifts Lumi analysed, so each year is scaled to one shift.

Raw count: 2017: 1 in 1 shift · 2020: 7 in 12 shifts · 2021: 7 in 24 shifts · 2022: 4 in 24 shifts · 2023: 5 in 12 shifts · 2024: 6 in 18 shifts · 2025: 3 in 8 shifts · 2026: 6 in 9 shifts.

Up to 2023: 0.4; a shift, of 25
Since 2024: 0.4; 0.0
Usual gap: 1.3 yrs; between years asking it
Shifts with it: 39/108; 36% of analysed shifts

Revise first

Bohr Radius Calculation · asked 2017, 2020, 2021, 2022, 2025, 2026
Ionization and Excitation Energy · asked 2021, 2022, 2023, 2024, 2026
Total, Kinetic, and Potential Energy · asked 2021, 2023, 2024, 2025

How it is asked

Difficulty, format and skill

Across all 39 questions on Bohr's Atomic Theory since 2017.

Difficulty

QUESTIONS

2216

Easy22 · 56%
Medium16 · 41%
Hard1 · 3%

Format

Numerical value · 18 Q46%
Single correct · 16 Q41%
Two statements · 3 Q8%
Other · 2 Q5%

Skill tested

Calculation · 28 Q72%
Conceptual · 5 Q13%
Multi-step · 3 Q8%
Application · 2 Q5%
Recall · 1 Q3%

Repeats

New idea, or one asked before?

Each column is a year. Blue questions tested an idea no earlier year had asked; navy ones went back to an idea from an earlier year. 2017 is the first year, so everything in it counts as new. Heights are question counts, and Lumi analysed 1 to 24 shifts a year, so compare the split inside a column rather than heights across years.

’17’20’21’22’23’24’25’26

Idea asked for the first time
Idea asked in an earlier year

Coverage of the topic

JEE Main has asked 14 of the 42 ideas in this topic. 24 have never been asked yet.

14424

Asked directly14 · 33%
Touched inside another question4 · 10%
Never asked24 · 57%

Ideas come from Lumi’s JEE syllabus map. A never-asked idea is not a safe skip: across all of JEE Main, 22% of questions since 2024 tested an idea no earlier year had asked.

Drill down

Idea, year, question

Every idea JEE Main tested in this topic, with its eight years. Open one to read the questions.

ideaAskedShareYears’17’20’21’22’23’24’25’26

OpenRepeated8 · 21%21%6/822
- 4 Apr ’26 S2 · Q52
  The species having identical radii according to the Bohr's theory are: A. H (first orbit) B. $\mathrm{He^+}$ (first orbit) C.…
  easyOtherAsked the year before
- 6 Apr ’26 S2 · Q52
  The Bohr radius of a hydrogen like species is 70.53 pm. The species and the stationary state ( $n$ ) are respectively (Given : Hydrogen atom…
  easySingle correctAsked the year before
- 2 Apr ’25 S1 · Q52
  According to Bohr's model of hydrogen atom, which of the following statement is incorrect ?
  easySingle correct
- 26 Jun ’22 S1 · Q63
  If 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 correctAsked the year before
- 3 Aug ’21 S2 · Q53
  The 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 valueAsked the year before
- 8 Jan ’20 S2 · Q29
  Read the question
  easySingle correctAsked the year before
- 5 Sep ’20 S1 · Q41
  Read the question
  mediumSingle correctAsked the year before
- 2017 · Q38
  Read the question
  easySingle correctNew idea
OpenRepeated6 · 15%15%5/82
OpenRepeated4 · 10%10%4/8
OpenRepeated3 · 8%8%3/8
OpenRepeated3 · 8%8%3/8
OpenRepeated3 · 8%8%3/8
OpenRepeated2 · 5%5%2/8
OpenRepeated2 · 5%5%2/8
OpenRepeated2 · 5%5%2/8
OpenRepeated2 · 5%5%2/8
Open1 · 3%3%1/8
Open1 · 3%3%1/8
Open1 · 3%3%1/8
Open1 · 3%3%1/8

Squares are the 8 years with analysed shifts, 2017 to 2026. A number is the questions that year when there is more than one; the shade is scaled to one shift, so a year with more analysed shifts (1 to 24 a year) does not look darker. Share is of the level above.

Ideas

Every idea inside this topic

14 different ideas were tested; 10 came more than once.

Bohr Radius Calculation8×
ratio of bohr orbit radii
Single correct · 8 shifts · 1 numerical
Ionization and Excitation Energy6×
ionization energy of hydrogen-like ion
Numerical value · 6 shifts · 5 numerical
Total, Kinetic, and Potential Energy4×
energy in excited state of hydrogen-like ion
Numerical value · 4 shifts · 2 numerical
Photoelectric Effect Coupling3×
wavelength from photoelectric data
Numerical value · 3 shifts · 3 numerical
Circumference and De Broglie Wavelength3×
de broglie wavelength in 4th orbit in units of pi a0
Numerical value · 3 shifts · 2 numerical
Angular Momentum Quantization3×
statement i/ii on bohr model
Numerical value · 3 shifts · 1 numerical
Longest and Shortest Wavelengths in a Series2×
ratio of wavelengths in spectral series
Other · 2 shifts
Rydberg Formula and Transitions2×
ratio of wave numbers of spectral lines
Single correct · 2 shifts
Electron Velocity in Orbit2×
electron velocity from rydberg energy
Numerical value · 2 shifts · 1 numerical
Number of Spectral Lines in Transitions2×
spectral lines between given levels
Numerical value · 2 shifts · 2 numerical
Limitations of Bohr Model1×
identify bohr postulate contradicting quantum mechanics
Single correct · 1 shift
Time Period and Frequency of Electron Revolution1×
de broglie wave frequency in first bohr orbit
Numerical value · 1 shift · 1 numerical
Limitations of Bohr's Model1×
statement i/ii on bohr model limitations
Two statements · 1 shift
Electromagnetic Regions of Spectral Series1×
region of spectral series
Single correct · 1 shift

Idea	Times	Shifts	Format	Numerical
Bohr Radius Calculationratio of bohr orbit radii	8	8	Single correctCalculation	1
Ionization and Excitation Energyionization energy of hydrogen-like ion	6	6	Numerical valueCalculation	5
Total, Kinetic, and Potential Energyenergy in excited state of hydrogen-like ion	4	4	Numerical valueCalculation	2
Photoelectric Effect Couplingwavelength from photoelectric data	3	3	Numerical valueCalculation	3
Circumference and De Broglie Wavelengthde broglie wavelength in 4th orbit in units of pi a0	3	3	Numerical valueCalculation	2
Angular Momentum Quantizationstatement i/ii on bohr model	3	3	Numerical valueCalculation	1
Longest and Shortest Wavelengths in a Seriesratio of wavelengths in spectral series	2	2	OtherConceptual	–
Rydberg Formula and Transitionsratio of wave numbers of spectral lines	2	2	Single correctCalculation	–
Electron Velocity in Orbitelectron velocity from rydberg energy	2	2	Numerical valueCalculation	1
Number of Spectral Lines in Transitionsspectral lines between given levels	2	2	Numerical valueCalculation	2
Limitations of Bohr Modelidentify bohr postulate contradicting quantum mechanics	1	1	Single correctConceptual	–
Time Period and Frequency of Electron Revolutionde broglie wave frequency in first bohr orbit	1	1	Numerical valueCalculation	1
Limitations of Bohr's Modelstatement i/ii on bohr model limitations	1	1	Two statementsConceptual	–
Electromagnetic Regions of Spectral Seriesregion of spectral series	1	1	Single correctRecall	–

Times and shifts count every analysed shift. Across JEE Main, 78% of questions since 2024 went back to an idea an earlier year had asked; the rest were new. All repeated ideas

Every question

Bohr's Atomic Theory questions, year by year

The opening words of each question as it appeared in the official paper, with the idea it tested. Open one for its options and the official answer.

Questions from the official JEE Main Paper 1 shifts published by NTA (CBSE for 2017). Questions NTA dropped are left out. Topic and idea tags, counts and notes are Lumi’s.

Key findings

Questions a shift, year by year

Difficulty, format and skill

Difficulty

Format

Skill tested

New idea, or one asked before?

Coverage of the topic

Idea, year, question

Every idea inside this topic

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