Question 1Multiple choice · 1 markA* challenge
Hydrogen atoms are excited to the n = 5 level. How many different photon wavelengths can be emitted as they return to the ground state?
- A 4
- B 5
- C 10
- D 25
Show answer
Answer: C
Free E.1 Structure of the atom questions for IB Physics (SL & HL), part of E Nuclear & quantum physics. Each question has the answer and the marking points an examiner would look for.
Generate a full E.1 Structure of the Atom worksheet →All E Nuclear & quantum physics questionsHydrogen atoms are excited to the n = 5 level. How many different photon wavelengths can be emitted as they return to the ground state?
Answer: C
In a Rutherford scattering experiment, alpha particles of energy 5.0 MeV are directed at a thin gold foil (Z = 79).
Calculate the distance of closest approach for a head-on collision.
State what can be deduced from the fact that most alpha particles pass straight through.
State what can be deduced from the few that are deflected through more than 90°.
Explain why alpha particles of much higher energy show deviations from Rutherford’s prediction.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | 4.5 × 10−14 m Ek = kq1q2/d ✓ d = 8.99 × 109 × 2 × 79 × (1.6 × 10−19)2/(5.0 × 1.6 × 10−13) ✓ = 4.5 × 10−14 m ✓ | 3 |
| (b) | mostly empty space the atom is mostly empty space ✓ | 1 |
| (c) | small, dense, positive nucleus mass and positive charge concentrated in a tiny nucleus ✓ | 1 |
| (d) | strong force they get close enough to the nucleus ✓ for the strong nuclear force to act ✓ | 2 |
Alpha particles of kinetic energy 4.0 MeV are directed at a thin silver foil (Z = 47).
Calculate the distance of closest approach for a head-on collision.
Outline why using alpha particles of much higher energy leads to deviations from Rutherford’s model.
A hydrogen emission line has wavelength 486 nm. Calculate the energy of the photon in eV.
Explain how emission spectra provide evidence for discrete atomic energy levels.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | 3.4 × 10−14 m Ek = kQq/r ✓ Q = 47e, q = 2e ✓ r = 3.4 × 10−14 m ✓ | 3 |
| (b) | strong nuclear force alpha particles get close enough to the nucleus ✓ that the strong nuclear force acts ✓ | 2 |
| (c) | 2.56 eV E = hc/λ = 4.09 × 10−19 J ✓ = 2.56 eV ✓ | 2 |
| (d) | specific wavelengths only specific wavelengths / photon energies are emitted ✓ each corresponds to a transition between fixed energy levels ✓ | 2 |
The energy levels of hydrogen are −13.6 eV, −3.40 eV, −1.51 eV and −0.85 eV (n = 1 to 4).
Explain why the hydrogen spectrum consists of discrete lines.
Calculate the wavelength of the photon emitted in the transition from n = 3 to n = 2, and state the region of the spectrum.
Determine the number of different wavelengths that could be emitted by atoms excited to n = 4.
A photon of energy 12.75 eV is absorbed by a hydrogen atom in the ground state. State the level the electron moves to.
Calculate the minimum frequency of radiation that can ionize hydrogen from the ground state.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | discrete energy levels electrons occupy discrete energy levels ✓ photons emitted have energies equal to the differences between levels, so only certain wavelengths ✓ | 2 |
| (b) | 658 nm, visible ΔE = 1.89 eV ✓ λ = hcΔE = 658 nm ✓ visible (red) ✓ | 3 |
| (c) | 6 6 ✓ | 1 |
| (d) | n = 4 n = 4 (−13.6 + 12.75 = −0.85 eV) ✓ | 1 |
| (e) | 3.28 × 1015 Hz E = 13.6 eV = hf ✓ f = 3.28 × 1015 Hz ✓ | 2 |
The energy levels of a hydrogen atom are −13.6, −3.40, −1.51 and −0.85 eV.
Calculate the wavelength of the photon emitted in the transition from −1.51 eV to −3.40 eV.
State how many different photon energies can be emitted by atoms excited to the −0.85 eV level.
Explain how this provides evidence for discrete energy levels.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | 658 nm ΔE = 1.89 eV = 3.02 × 10−19 J ✓ λ = 658 nm ✓ | 2 |
| (b) | 6 6 ✓ | 1 |
| (c) | only specific wavelengths only specific wavelengths (line spectrum) are emitted ✓ corresponding to differences between fixed energy levels ✓ | 2 |
A hydrogen emission spectrum contains a line of wavelength 486 nm.
Calculate the energy of the photon, in eV.
Distinguish between an emission spectrum and an absorption spectrum.
Explain why the spectrum consists of discrete lines.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | 2.6 eV E = hc/λ = 4.09 × 10−19 J ✓ = 2.56 eV ✓ | 2 |
| (b) | bright lines vs dark lines emission: bright lines on a dark background from excited atoms ✓ absorption: dark lines in a continuous spectrum where photons are absorbed ✓ | 2 |
| (c) | discrete energy levels electrons occupy discrete energy levels, so only specific photon energies are emitted ✓ | 1 |
Riyaz Shaikh has mentored IGCSE, IB and A Level students for 15+ years, one-on-one, online and in Mumbai. The hardest questions on this site are the ones he uses to find a student's weak points.
Meet Riyaz →Original IB-style practice questions written for mentorriyaz.in. These are not IB past paper questions, and this site is not affiliated with or endorsed by the International Baccalaureate Organization. Updated 2026-11-04. Paper generator · mentorriyaz.in