AS · Practice questions · The atom and radiation

A dense little nucleus.

Six original Cambridge-style questions on alpha-scattering, notation, and decay equations.

Original questions All questions on this page are original work, written in the Cambridge AS & A Level style. They are not from past papers. They test the same concepts and skills the syllabus rewards.

Keep these straight

Balance A and Z.

Notation: A nucleons, Z protons.
Conserved: A and Z balance.
Alpha: A−4, Z−2.

Analysis

[2 marks]

State the main conclusion drawn from the alpha-particle scattering experiment.

Almost all the mass and all the positive charge of an atom are concentrated in a tiny nucleus ✓
and the atom is mostly empty space ✓

Analysis

[2 marks]

For the nuclide carbon-14 (A = 14, Z = 6), state the number of protons and neutrons.

Protons = Z = 6 ✓
Neutrons = A − Z = 14 − 6 = 8 ✓

Analysis

[3 marks]

Radium-226 (Z = 88) decays by alpha emission. Write the nucleon and proton numbers of the daughter nucleus and of the alpha particle, and show that they balance.

Daughter: A = 226 − 4 = 222, Z = 88 − 2 = 86 (radon) ✓
Alpha particle: A = 4, Z = 2 ✓
Check: 222 + 4 = 226 and 86 + 2 = 88, so both balance ✓

Analysis

[3 marks]

Carbon-14 (Z = 6) decays by beta-minus emission to nitrogen. State the nucleon and proton numbers of the daughter nucleus and explain the change in Z.

Daughter: A = 14 (unchanged), Z = 6 + 1 = 7 (nitrogen) ✓
A neutron changes into a proton, so the proton number rises by one while the nucleon number stays the same ✓

Analysis

[2 marks]

Compare the penetrating power of alpha and gamma radiation.

Alpha is the least penetrating, stopped by paper or a few centimetres of air ✓
Gamma is the most penetrating, needing thick lead or concrete to reduce it significantly ✓

Analysis

[2 marks]

Define the term isotope.

Isotopes are atoms of the same element (same proton number) ✓
but with different numbers of neutrons, and hence different nucleon numbers ✓

Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.