A Level Physics 11.1 Atoms, Nuclei and Radiation MCQs – 30 Practice Questions with Answers (Cambridge 9702)

These 30 original multiple-choice questions cover Cambridge AS & A Level Physics 9702 Section 11.1, Atoms, Nuclei and Radiation, from atomic structure and nuclide notation through the properties of α, β and γ radiation to decay equations and Rutherford scattering. Work through each question, then open the Show Answer toggle to check your answer and read a full explanation.

Formula recap: Neutron number N = A − Z. In any nuclear equation the total nucleon number A and the total proton number Z balance on both sides. Keep every key equation for this topic in one place on our A Level Physics Formula Sheet.

Atomic Structure & Nuclides

Q1. Which statement about the structure of the atom is correct?

  • (A) The nucleus occupies most of the volume of the atom
  • (B) The nucleus is tiny compared with the atom but contains almost all of the atom’s mass
  • (C) The nucleus is electrically neutral overall
  • (D) Electrons are embedded inside the nucleus
Show Answer

Answer: B – The nucleus (protons and neutrons) has a diameter of about 10−14 m compared with about 10−10 m for the atom, yet it holds nearly all the mass; the electrons occupy the space around it.

Q2. The proton number Z of a nucleus is defined as the number of

  • (A) neutrons in the nucleus
  • (B) protons plus neutrons in the nucleus
  • (C) protons in the nucleus
  • (D) electrons in a neutral atom plus neutrons
Show Answer

Answer: C – Z is the number of protons. It fixes the element and, in a neutral atom, equals the number of electrons.

Q3. A nucleus is represented by 5626Fe. How many neutrons does it contain?

  • (A) 30
  • (B) 26
  • (C) 56
  • (D) 82
Show Answer

Answer: A – Neutron number = A − Z = 56 − 26 = 30.

Q4. A neutral aluminium atom, 2713Al, loses three electrons to form an Al3+ ion. How many electrons remain in the ion?

  • (A) 13
  • (B) 16
  • (C) 24
  • (D) 10
Show Answer

Answer: D – Ionisation changes only the electron number: 13 − 3 = 10 electrons. The nucleus (13 protons, 14 neutrons) is unchanged.

Q5. Isotopes of the same element are nuclei that have

  • (A) the same nucleon number but different proton numbers
  • (B) the same proton number but different neutron numbers
  • (C) the same neutron number but different proton numbers
  • (D) different proton numbers and different chemical properties
Show Answer

Answer: B – Isotopes share Z (so they are the same element, with identical chemical properties) but have different numbers of neutrons, hence different masses.

Q6. How many neutrons are there in a nucleus of carbon-14, 146C?

  • (A) 6
  • (B) 14
  • (C) 8
  • (D) 20
Show Answer

Answer: C – Neutrons = A − Z = 14 − 6 = 8.

Q7. Which value is the best estimate of the diameter of a typical atomic nucleus?

  • (A) 10−14 m
  • (B) 10−10 m
  • (C) 10−18 m
  • (D) 10−7 m
Show Answer

Answer: A – Nuclei are of order 10−14 m across, while atoms are of order 10−10 m, so the nucleus is about 10,000 times smaller than the atom.

Q8. A sulfide ion is formed when a neutral sulfur atom, 3216S, gains two electrons. How many electrons does the S2− ion contain?

  • (A) 14
  • (B) 16
  • (C) 32
  • (D) 18
Show Answer

Answer: D – Gaining electrons changes only the electron count: 16 + 2 = 18 electrons.

Q9. Which pair of nuclei are isotopes of the same element?

  • (A) 146C and 147N
  • (B) 146C and 156C
  • (C) 126C and 168O
  • (D) 4019K and 4020Ca
Show Answer

Answer: B – Both have Z = 6 (carbon) but different nucleon numbers (14 and 15), so they are isotopes.

Q10. How many electrons are there in a neutral atom of sodium, 2311Na?

  • (A) 23
  • (B) 12
  • (C) 11
  • (D) 34
Show Answer

Answer: C – A neutral atom has the same number of electrons as protons, so electrons = Z = 11 (the 12 is the neutron number).

Alpha, Beta & Gamma Radiation

Q11. An α-particle is identical to

  • (A) a helium nucleus containing 2 protons and 2 neutrons
  • (B) a fast-moving electron
  • (C) a hydrogen nucleus containing 1 proton
  • (D) an electromagnetic wave of very short wavelength
Show Answer

Answer: A – An α-particle is 42He: 2 protons and 2 neutrons, carrying charge +2e.

Q12. Which type of radiation is the most strongly ionising?

  • (A) γ radiation
  • (B) β radiation
  • (C) ultraviolet radiation
  • (D) α radiation
Show Answer

Answer: D – α-particles are heavy and doubly charged, so they ionise atoms very strongly along a short track; γ radiation is the least ionising of the three nuclear radiations.

Q13. Which material will stop β radiation completely?

  • (A) A single sheet of paper
  • (B) A few millimetres of aluminium
  • (C) Several metres of air only, with no solid absorber
  • (D) A thin sheet of lead foil a fraction of a millimetre thick is essential
Show Answer

Answer: B – β-particles pass through paper but are stopped by a few millimetres of aluminium; lead also stops them but is far more than is needed.

Q14. A beam of γ radiation passes through a strong magnetic field without being deflected. This is because γ radiation

  • (A) travels too fast to be deflected
  • (B) has a very large mass
  • (C) carries no electric charge
  • (D) is deflected only by electric fields
Show Answer

Answer: C – A magnetic force acts only on a moving charge. Gamma radiation is an electromagnetic wave with no charge, so it travels straight through both electric and magnetic fields.

Q15. In β− decay, the emitted electron

  • (A) is created in the nucleus when a neutron changes into a proton
  • (B) was orbiting the nucleus and is knocked out
  • (C) comes from the breakdown of a proton
  • (D) is an electron that was stored inside a neutron as a separate particle
Show Answer

Answer: A – A neutron in the nucleus changes into a proton, an electron and an antineutrino: n → p + e− + antineutrino. The electron is created at the moment of decay and ejected at high speed.

Q16. What is the approximate range of α-particles in air?

  • (A) A few millimetres
  • (B) Several metres
  • (C) Unlimited, like γ radiation
  • (D) A few centimetres
Show Answer

Answer: D – Because they ionise so strongly, α-particles lose energy quickly and travel only a few centimetres in air before stopping.

Q17. The charge on a β− particle is

  • (A) +2e
  • (B) −e
  • (C) zero
  • (D) +e
Show Answer

Answer: B – A β− particle is an electron, charge −e = −1.6 × 10−19 C.

Q18. Beams of α and β radiation pass through the same electric field. The α beam is deflected much less than the β beam mainly because an α-particle has

  • (A) a much smaller charge than a β-particle
  • (B) no charge at all
  • (C) a much larger mass, so its path curves far less for a comparable force
  • (D) a much higher speed at all times
Show Answer

Answer: C – The α-particle actually has twice the charge (2e), but its mass is roughly 7,000 times the electron mass, so the acceleration it experiences is far smaller and its deflection is much less.

Q19. In a cloud chamber, short, thick, straight tracks are produced by

  • (A) γ radiation
  • (B) β radiation
  • (C) X-rays
  • (D) α radiation
Show Answer

Answer: D – Strong ionisation makes dense (thick) tracks, the short range keeps them short, and the large mass means collisions barely change the direction, so the tracks are straight.

Q20. Which statement about γ radiation is correct?

  • (A) It is an electromagnetic wave that travels at the speed of light in a vacuum
  • (B) It is stopped completely by a sheet of paper
  • (C) It consists of slow-moving electrons
  • (D) It has a range of only a few centimetres in air
Show Answer

Answer: A – Gamma radiation is high-energy electromagnetic radiation: uncharged, weakly ionising, travelling at c, and only reduced in intensity by thick lead or concrete.


Nuclear Changes & Rutherford Scattering

Q21. Radium-226 decays by α emission: 22688Ra → ? + 42He. The daughter nucleus is

  • (A) 23090Th
  • (B) 22288Ra
  • (C) 22286Rn
  • (D) 22686Rn
Show Answer

Answer: C – Alpha emission reduces A by 4 (226 − 4 = 222) and Z by 2 (88 − 2 = 86), giving radon-222. Check: 222 + 4 = 226 and 86 + 2 = 88, so the equation balances.

Q22. When a nucleus undergoes β− decay, its proton number and nucleon number change as follows:

  • (A) Z increases by 1, A stays the same
  • (B) Z decreases by 1, A stays the same
  • (C) Z stays the same, A decreases by 1
  • (D) Z increases by 1, A increases by 1
Show Answer

Answer: A – A neutron changes into a proton, so the proton number rises by 1 while the total number of nucleons is unchanged.

Q23. Plutonium-239 decays by α emission: 23994Pu → X + 42He. The nucleus X is

  • (A) 24396Cm
  • (B) 23594Pu
  • (C) 23992U
  • (D) 23592U
Show Answer

Answer: D – A: 239 − 4 = 235; Z: 94 − 2 = 92, so X is uranium-235. Check: 235 + 4 = 239 and 92 + 2 = 94.

Q24. Which equation correctly represents β− decay inside the nucleus?

  • (A) p → n + e− + antineutrino
  • (B) n → p + e− + antineutrino
  • (C) n → p + e+ + neutrino
  • (D) p + e− → n + antineutrino
Show Answer

Answer: B – In β− decay a neutron changes into a proton, an electron and an antineutrino. Nucleon number balances (1 = 1) and charge balances (0 = +1 − 1).

Q25. A nucleus emits a γ ray. What happens to its nucleon number A and proton number Z?

  • (A) A decreases by 4 and Z decreases by 2
  • (B) A stays the same and Z increases by 1
  • (C) Both A and Z stay the same
  • (D) A decreases by 1 and Z stays the same
Show Answer

Answer: C – Gamma emission is just the release of energy from an excited nucleus; no particles are lost, so A and Z are unchanged and the element stays the same.

Q26. In Rutherford’s scattering experiment, most α-particles passed straight through thin gold foil with little or no deflection. This showed that

  • (A) most of the atom is empty space
  • (B) the nucleus fills most of the atom
  • (C) the positive charge is spread evenly through the atom
  • (D) α-particles are not affected by electric fields
Show Answer

Answer: A – The α-particles met nothing massive or strongly charged on their path, so almost all of the atom’s volume must be empty space, with the mass concentrated in a tiny nucleus.

Q27. In the Rutherford experiment, a very small fraction of α-particles were deflected through angles greater than 90°. This large-angle deflection is evidence that the nucleus is

  • (A) large and weakly charged
  • (B) spread throughout the atom
  • (C) negatively charged
  • (D) tiny, massive and positively charged
Show Answer

Answer: D – Only a very small, dense, positively charged centre can repel an approaching α-particle strongly enough to turn it back through a large angle.

Q28. Carbon-14 undergoes β− decay. The completed equation is 146C → ? + 0−1e, where the missing nucleus is

  • (A) 145B
  • (B) 147N
  • (C) 104Be
  • (D) 146C
Show Answer

Answer: B – A is unchanged (14) and Z increases by 1 (6 → 7), giving nitrogen-14. Check: 14 = 14 + 0 and 6 = 7 + (−1).

Q29. A nucleus emits an α-particle and then a second α-particle. The overall change in A and Z is

  • (A) A −4, Z −2
  • (B) A −8, Z −2
  • (C) A −8, Z −4
  • (D) A unchanged, Z −4
Show Answer

Answer: C – Each α emission removes 4 nucleons and 2 protons, so two emissions give A −8 and Z −4.

Q30. Uranium-238, 23892U, decays by α emission followed by β− emission from the daughter nucleus. The proton number of the final nucleus is

  • (A) 91
  • (B) 90
  • (C) 92
  • (D) 89
Show Answer

Answer: A – Alpha emission: Z = 92 − 2 = 90. Beta-minus emission then raises Z by 1: 90 + 1 = 91 (and A stays at 234 after the alpha step).

Keep practising: Browse the full Physics MCQs hub for more Cambridge 9702 topic pages, and use the A Level Physics Formula Sheet to revise the key equations before your exam.

All questions on this page are original practice questions written for Quaidianpoint.com. They are not Cambridge past-paper questions, and this page is not affiliated with or endorsed by Cambridge Assessment International Education.