The nuclear model of the atom: IGCSE Physics questions with answers
Free The nuclear model of the atom questions for IGCSE Physics (0625), part of Nuclear physics. Each question has the answer and the marking points an examiner would look for.
In the alpha-particle scattering experiment, alpha particles are fired at a thin sheet of gold foil. 1 A very small number bounce back, so the nucleus is very small, dense and positively charged. 2 Some alpha particles are deflected because they are attracted by the nucleus. 3 Most alpha particles pass straight through, so most of the atom is empty space. Which statements are correct?
A 1, 2 and 3
B 1 and 3 only
C 1 only
D 3 only
Show answer
Answer: B
Question 2Multiple choice · 1 mark
What are isotopes of an element?
A atoms with different numbers of electrons
B atoms with the same number of protons but different numbers of neutrons
C atoms that are radioactive
D atoms with the same number of neutrons but different numbers of protons
Show answer
Answer: B
Question 3Structured · 5 marksA* challenge
In the alpha-particle scattering experiment, alpha particles were fired at a thin gold foil.
(a)
Describe what was observed.
[3]
(b)
State what each observation shows about the atom.
[2]
Show answers and mark scheme
Part
Answer and marking points
Marks
(a)
most passed through; some deflected; few bounced back
most alpha particles passed straight through B1 some were deflected through small angles B1 a very few were deflected back (through large angles) B1
3
(b)
mostly empty space; small dense positive nucleus
most of the atom is empty space B1 the mass and positive charge are concentrated in a tiny nucleus B1
2
Question 4Structured · 10 marks
This question is about the nucleus.
(a)
In the alpha-particle scattering experiment, most alpha particles passed straight through gold foil and a very few bounced back. State what each observation shows about the atom.
[2]
(b)
A nucleus of uranium-238 has proton number 92. State the number of neutrons.
[1]
(c)
Uranium-238 decays by alpha emission to thorium. Write the nuclide equation for the decay.
[3]
(d)
State what happens in a nucleus during beta decay.
[2]
(e)
Explain the difference between nuclear fission and nuclear fusion.
[2]
Show answers and mark scheme
Part
Answer and marking points
Marks
(a)
most of atom is empty space; small dense positively charged nucleus
most of the atom is empty space B1 mass and positive charge are concentrated in a very small nucleus B1
2
(b)
146
146 B1
1
(c)
23892U → 23490Th + 42He
alpha particle as 42He / α B1 nucleon number of product 234 B1 proton number of product 90 B1
3
(d)
neutron changes into a proton and an electron; electron emitted
a neutron changes into a proton B1 and an electron (beta particle) is emitted from the nucleus B1
2
(e)
fission: large nucleus splits; fusion: small nuclei join
fission: a large (unstable) nucleus splits into two smaller nuclei B1 fusion: two light nuclei join to form a heavier nucleus B1
2
Question 5Structured · 5 marks
An atom of sodium has a nucleon number of 23 and a proton number of 11.
(a)
State the number of protons, neutrons and electrons in a neutral atom.
[3]
(b)
State what is meant by isotopes.
[2]
Show answers and mark scheme
Part
Answer and marking points
Marks
(a)
11, 12, 11
protons 11 B1 neutrons 12 B1 electrons 11 B1
3
(b)
same protons, different neutrons
atoms of the same element (same number of protons) B1 with different numbers of neutrons B1
2
Question 6Structured · 10 marks
This question is about nuclear energy.
(a)
Describe what happens when a nucleus of uranium-235 undergoes fission.
[3]
(b)
Explain how a chain reaction occurs, and why it must be controlled in a reactor.
[3]
(c)
Give two disadvantages of generating electricity using nuclear fission.
[2]
(d)
Nuclear waste from reactors contains isotopes with half-lives of thousands of years. Explain why this makes storage difficult.
[2]
Show answers and mark scheme
Part
Answer and marking points
Marks
(a)
absorbs a neutron; splits into two smaller nuclei; releases 2–3 neutrons and energy
the nucleus absorbs a neutron B1 splits into two smaller nuclei (daughter nuclei) B1 releasing two or three neutrons and energy B1
3
(b)
released neutrons cause further fissions; uncontrolled → rate of fission rises rapidly, overheating / meltdown; control rods absorb neutrons
neutrons released cause further fissions B1 the number of fissions could increase rapidly B1 control rods absorb neutrons so that on average one neutron from each fission causes another B1
3
(c)
radioactive waste, long half-life; risk of accidents; high cost of decommissioning
Any 2 of: radioactive waste that remains dangerous for a long time; risk of accidents releasing radiation; high building / decommissioning costs B2
2
(d)
remains highly active for very long; must be isolated and secure for thousands of years
the activity falls very slowly so it stays dangerous B1 it must be stored securely and isolated for thousands of years B1
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Original Cambridge-style practice questions written for mentorriyaz.in. These are not Cambridge past paper questions, and this site is not affiliated with or endorsed by Cambridge University Press & Assessment. Updated 2026-11-04. Paper generator · mentorriyaz.in