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Atoms is a small chapter built almost entirely on the Bohr model, and NEET(UG) asks from it nearly every year. Three formulas carry the whole thing: the radius goes as n2, the energy as −13.6/n2, and the speed as 1/n. If you know those three and the names of the spectral series, you can answer almost anything the paper puts here. Ten questions below. Give them ten honest minutes.
What this chapter carries in NEET(UG)
- Usually 1 to 2 questions every year, which is 4 to 8 marks.
- Bohr radius, energy levels and the spectral series are the regular ones.
- Rutherford scattering and angular momentum quantisation come up as recall.
What the syllabus says
In the syllabus (Unit 18, Atoms and Nuclei): The alpha-particle scattering experiment, Rutherford’s model of the atom, the Bohr model, energy levels and the hydrogen spectrum.
Taken from the NMC syllabus for NEET (UG) 2026, the latest one published. See the full syllabus, unit by unit.
Formulas you must know by heart
| Bohr quantisation | mvr = nh/2π |
| Radius of the nth orbit | rn = 0.53 n2/Z Å |
| Speed in the nth orbit | vn = c/(137 n) × Z |
| Energy of the nth level | En = − 13.6 Z2/n2 eV |
| Energy of a transition | ΔE = 13.6 (1/n12 − 1/n22) eV |
| Rydberg formula | 1/λ = R (1/n12 − 1/n22) |
| Rydberg constant | R = 1.097 × 107 m−1 |
| Spectral series | Lyman n1 = 1 (ultraviolet), Balmer n1 = 2 (visible), Paschen n1 = 3 (infrared) |
| Number of spectral lines | n(n − 1)/2 |
The minus sign in front of 13.6 is not decoration. It says the electron is bound — you must put energy in to pull it away. Zero energy means a free electron at rest, which is why the ionisation energy of hydrogen is exactly 13.6 eV.
Ten questions. Give yourself ten minutes.
Write your answers down before you scroll. A question you looked up is a question you have not answered.
Q1. Rutherford’s alpha particle scattering experiment showed that
- (a) electrons move in fixed orbits
- (b) an atom has a small, heavy, positively charged nucleus
- (c) atoms cannot be divided
- (d) the nucleus contains neutrons
Q2. In Bohr’s model, the angular momentum of an electron in the nth orbit is
- (a) nh
- (b) nh/2π
- (c) nh/4π
- (d) h/2πn
Q3. The radius of the first Bohr orbit of hydrogen is 0.53 Å. The radius of the second orbit is
- (a) 1.06 Å
- (b) 2.12 Å
- (c) 0.265 Å
- (d) 4.77 Å
Q4. The energy of the n = 2 level of the hydrogen atom is
- (a) −13.6 eV
- (b) −3.4 eV
- (c) −1.51 eV
- (d) −0.85 eV
Q5. The energy needed to remove the electron completely from a hydrogen atom in its ground state is
- (a) 3.4 eV
- (b) 13.6 eV
- (c) 1.51 eV
- (d) 27.2 eV
Q6. The series of the hydrogen spectrum that falls in the visible region is the
- (a) Lyman series
- (b) Balmer series
- (c) Paschen series
- (d) Brackett series
Q7. The Lyman series of hydrogen lies in the
- (a) visible region
- (b) ultraviolet region
- (c) infrared region
- (d) X-ray region
Q8. If the speed of the electron in the first Bohr orbit is c/137, its speed in the second orbit is
- (a) c/137
- (b) c/274
- (c) 2c/137
- (d) c/68.5
Q9. The shortest wavelength of the Lyman series is emitted in a transition from
- (a) n = 2 to n = 1
- (b) n = ∞ to n = 1
- (c) n = 3 to n = 2
- (d) n = ∞ to n = 2
Q10. The value of the Rydberg constant is about
- (a) 1.097 × 107 m−1
- (b) 6.63 × 10−34 J·s
- (c) 9.1 × 10−31 kg
- (d) 1.6 × 10−19 C
Answer key, with a hint for each
| Q1 | (b) | A few alpha particles bounced almost straight back, which can only happen if nearly all the mass and charge sit in a tiny centre. |
| Q2 | (b) | mvr = nh/2π. This single assumption is what makes the orbits discrete. |
| Q3 | (b) | r ∝ n2, so r2 = 0.53 × 4. |
| Q4 | (b) | E2 = −13.6/4. |
| Q5 | (b) | That is the ionisation energy, the energy gap from the ground state up to zero. |
| Q6 | (b) | Balmer, with n1 = 2. Lyman is ultraviolet and Paschen is infrared. |
| Q7 | (b) | Lyman transitions end at n = 1 and carry the largest energy, so the shortest wavelengths. |
| Q8 | (b) | v ∝ 1/n, so the second orbit has half the speed. |
| Q9 | (b) | Shortest wavelength means largest energy, which is the jump from infinity down to the first level. |
| Q10 | (a) | Keep it apart from Planck’s constant and the electron mass, which are the usual distractors here. |
Now mark yourself honestly
NEET(UG) marks the way it marks. Use the same rule here:
- +4 for a right answer
- −1 for a wrong one
- 0 for a blank
So ten questions here are out of 40. In the real paper, 45 Physics questions are out of 180.
If you scored 32 or more, the basics of this chapter are secure. Move to harder questions, not more of these.
If you scored below 24, do not feel bad about it. You have just found out something useful before the exam did. Go back to the formula table above, learn it properly, and sit these ten again tomorrow.
And if you guessed a few and they landed, count those as wrong. A guess that works once will not work in May.
The full chapter, on a clock
Ten questions tell you a little. Forty-five tell you the truth.
The Beginner paper for Atoms is waiting for you on the portal: 45 questions, 45 minutes, marked out of 180, with the answer key and a hint for every question. Sit it tonight and you will know exactly where this chapter stands.
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