GCSE PhysicsAQA, Edexcel and OCR
38 physics questions on atomic structure. Pick your answer, then tap to see if you were right and why. Every answer comes from the Show Working science bank, checked against the GCSE content every board in England teaches.
01 / Quiz yourselfTry it, then tap to check
Choose your answer before you open it. Then read why, so it sticks.
01 / Atomic structureBoth tiers
Answer: A A positively charged nucleus
An atom has a tiny nucleus with a positive charge at its centre, surrounded by negatively charged electrons. Almost all of the mass of the atom is in the nucleus.
Checked against AQA GCSE Physics 8463 specification, 4.4.1.1 The structure of an atom
02 / Atomic structureBoth tiers
Answer: C It is much smaller
The nucleus is at least 10 000 times smaller in radius than the atom. The electrons move far outside it, so most of the atom is empty space.
Checked against AQA GCSE Physics 8463 specification, 4.4.1.1 The structure of an atom
03 / Atomic structureBoth tiers
Answer: C 10⁻¹⁰ m
Atoms are about 10⁻¹⁰ m in size (order of magnitude), and small molecules are of a similar order of size. A nucleus is far smaller still, and even a bacterium, about 10⁻⁶ m long, is thousands of times bigger than an atom.
Checked against OCR Gateway Physics A J249 specification, P1.1c The particle model
04 / Atomic structureBoth tiers
Answer: B A ball of positive charge with electrons in it
The discovery of the electron showed that atoms contain smaller, negative particles. The plum pudding model pictured the atom as a ball of positive charge with negative electrons dotted through it.
Checked against AQA GCSE Physics 8463 specification, 4.4.1.3 The development of the model of the atom
05 / Atomic structureBoth tiers
Answer: D Most of the atom is empty space
In the alpha particle scattering experiment, most alpha particles passed straight through, so the atom is mostly empty space. A few were deflected by large angles: they had come close to a tiny, positive nucleus holding most of the mass, which repelled them.
Checked against AQA GCSE Physics 8463 specification, 4.4.1.3 The development of the model of the atom
06 / Atomic structureBoth tiers
Answer: A Mass and positive charge are in a tiny nucleus
In the plum pudding model the positive charge fills the whole atom. In the nuclear model the positive charge and almost all the mass are in a tiny nucleus, with electrons around it. Models are changed or replaced when new experimental evidence does not fit them.
Checked against AQA GCSE Physics 8463 specification, 4.4.1.3 The development of the model of the atom
07 / Atomic structureBoth tiers
Answer: A Electrons orbit at set distances from the nucleus
The plum pudding model came first. Alpha scattering led to the nuclear model. Bohr then suggested that electrons orbit the nucleus at fixed distances, in energy levels, and his calculations agreed with experiments, so the idea was accepted.
Checked against AQA GCSE Physics 8463 specification, 4.4.1.3 The development of the model of the atom
08 / Atomic structureBoth tiers
Answer: C Protons and neutrons
The nucleus is made of protons and neutrons. A proton has a relative charge of +1 and a neutron has no charge; both have a relative mass of 1. Electrons, outside the nucleus, have a charge of −1 and a very small mass.
Checked against AQA GCSE Physics 8463 specification, 4.4.1.1 The structure of an atom
09 / Atomic structureBoth tiers
Answer: A It has equal numbers of protons and electrons
Every nucleus of an element has the same number of protons, so each element has its own nuclear charge. In an atom the number of electrons equals the number of protons, so their charges cancel and the atom is neutral.
Checked against AQA GCSE Physics 8463 specification, 4.4.1.2 Mass number, atomic number and isotopes
10 / Atomic structureBoth tiers
Answer: C Atoms of an element with different numbers of neutrons
Isotopes are atoms of the same element, so they have the same number of protons and the same nuclear charge. They have different numbers of neutrons, so their nuclei have different masses.
Checked against AQA GCSE Physics 8463 specification, 4.4.1.2 Mass number, atomic number and isotopes
11 / Atomic structureBoth tiers
Answer: C The number of protons
In a nuclear symbol the top number is the mass number: protons plus neutrons. The bottom number is the atomic number: the number of protons, which gives the charge of the nucleus and fixes the element.
Checked against AQA GCSE Physics 8463 specification, 4.4.1.2 Mass number, atomic number and isotopes
12 / Atomic structureBoth tiers
Answer: D Isotopes of uranium
Isotopes share the same atomic number (bottom number), so they are the same element with the same nuclear charge. Their mass numbers (top numbers) differ because they have different numbers of neutrons.
Checked against OCR Gateway Physics A J249 specification, P6.1c Radioactive emissions
13 / Atomic structureBoth tiers
Answer: A It moves further from the nucleus
Electrons are arranged at different distances from the nucleus, in energy levels. Absorbing electromagnetic radiation can move an electron further out, to a higher level. When it drops back closer to the nucleus, it emits electromagnetic radiation.
Checked against AQA GCSE Physics 8463 specification, 4.4.1.1 The structure of an atom
14 / Atomic structureBoth tiers
Answer: B It loses one or more outer electrons
If an atom loses one or more outer electrons, it has more protons than electrons, so it becomes a positive ion. Ionising radiation does this by knocking electrons out of atoms. It does not make the atoms radioactive.
Checked against OCR Gateway Physics A J249 specification, P6.1h Radioactive emissions
15 / Atomic structureBoth tiers
Answer: A They are unstable
Some nuclei are unstable. They give out radiation as they change to become more stable. This radioactive decay is random: you cannot predict when any one nucleus will decay, and heating or squeezing it does not change that.
Checked against AQA GCSE Physics 8463 specification, 4.4.2.1 Radioactive decay and nuclear radiation
16 / Atomic structureBoth tiers
Answer: C Two protons and two neutrons
An alpha particle is two protons and two neutrons stuck together, which is the same as a helium nucleus. It has no electrons, so it is not a helium atom.
Checked against AQA GCSE Physics 8463 specification, 4.4.2.1 Radioactive decay and nuclear radiation
17 / Atomic structureBoth tiers
Answer: C A fast electron from the nucleus
A beta particle is a high-speed electron thrown out of the nucleus, not one of the atom’s outer electrons. It is made when a neutron in the nucleus turns into a proton.
Checked against AQA GCSE Physics 8463 specification, 4.4.2.1 Radioactive decay and nuclear radiation
18 / Atomic structureBoth tiers
Answer: B Electromagnetic radiation from the nucleus
A gamma ray is electromagnetic radiation given out by a nucleus. It has no mass and no charge, so emitting it changes neither the mass nor the charge of the nucleus. The nucleus just loses some energy.
Checked against AQA GCSE Physics 8463 specification, 4.4.2.2 Nuclear equations
19 / Atomic structureBoth tiers
Answer: B Mass number falls by 4, atomic number by 2
Alpha decay takes 2 protons and 2 neutrons away, so the mass number falls by 4 and the atomic number by 2. In beta decay a neutron becomes a proton, so the atomic number rises by 1 and the mass number stays the same.
Checked against AQA GCSE Physics 8463 specification, 4.4.2.2 Nuclear equations
20 / Atomic structureBoth tiers
Answer: D Mass number falls by 1, atomic number stays the same
A neutron has a mass number of 1 and no charge. When a nucleus emits one, its mass number falls by 1, but it keeps the same number of protons, so its atomic number and the element stay the same.
Checked against OCR Twenty First Century Physics B J259 specification, P5.1 What is radioactivity?
21 / Atomic structureBoth tiers
Answer: C Its number of protons has changed
The element is fixed by the number of protons. Alpha and beta decay both change the number of protons, so the nucleus becomes a different element. Gamma emission does not, and neither does emitting a neutron.
Checked against AQA GCSE Physics 8463 specification, 4.4.2.2 Nuclear equations
22 / Atomic structureBoth tiers
Answer: C The totals of the mass numbers and of the atomic numbers
In a nuclear equation the mass numbers (top) must add up to the same total on each side, and so must the atomic numbers (bottom). The elements change, so you do not balance atoms of each element as in a chemical equation.
Checked against AQA GCSE Physics 8463 specification, 4.4.2.2 Nuclear equations
23 / Atomic structureBoth tiers
Answer: C ⁴₂He
An alpha particle is written ⁴₂He: mass number 4 and atomic number 2, like a helium nucleus. A beta particle is written ⁰₋₁e: an electron has almost no mass and a charge of −1.
Checked against AQA GCSE Physics 8463 specification, 4.4.2.2 Nuclear equations
24 / Atomic structureBoth tiers
Answer: A Time for the number of unstable nuclei to halve
The half-life is the time for the number of unstable nuclei in a sample to halve, or for its activity or count rate to fall to half. It is not half the time the material stays radioactive.
Checked against AQA GCSE Physics 8463 specification, 4.4.2.3 Half-lives and the random nature of radioactive decay
25 / Atomic structureBoth tiers
Answer: B Radioactive decay is random
Each nucleus decays at random, so you cannot say when one will go. But a sample has a huge number of nuclei, so the fraction that decays in a given time is very predictable. Half-life describes that.
Checked against Pearson Edexcel GCSE Physics 1PH0 specification, Topic 6 Radioactivity, 6.25 and 6.26
26 / Atomic structureBoth tiers
Answer: D It is the same as before
As nuclei decay, fewer unstable nuclei are left, so the activity falls over time. The half-life of an isotope stays the same: it takes the same time to halve again, whatever the starting amount.
Checked against AQA GCSE Physics 8463 specification, 4.4.2.3 Half-lives and the random nature of radioactive decay
27 / Atomic structureBoth tiers
Answer: C Alpha particles
Alpha particles are stopped by a sheet of paper or by skin. Beta particles pass through paper but are stopped by a few millimetres of aluminium. Gamma rays are the most penetrating: thick lead or concrete only reduces them.
Checked against OCR Gateway Physics A J249 specification, P6.1l Radioactive emissions
28 / Atomic structureBoth tiers
Answer: C Alpha
Alpha particles have a very short range in air, only a few centimetres, because they lose their energy quickly. Beta particles go further, and gamma rays travel a long way through air.
Checked against AQA GCSE Physics 8463 specification, 4.4.2.1 Radioactive decay and nuclear radiation
29 / Atomic structureBoth tiers
Answer: C Exposing an object to radiation from a source outside it
Irradiation means being exposed to radiation from a source outside; the object does not become radioactive. Contamination means radioactive atoms have got onto or into something. The hazard then comes from those atoms decaying.
Checked against AQA GCSE Physics 8463 specification, 4.4.2.4 Radioactive contamination
30 / Atomic structureBoth tiers
Answer: B The source stays and keeps emitting radiation
Contamination stays until it is removed or decays, so exposure goes on. Inside the body, alpha is most hazardous because all of it is absorbed by nearby cells, and it is strongly ionising. Outside the body, alpha is stopped by the skin and air.
Checked against OCR Twenty First Century Physics B J259 specification, P5.2 How can radioactive materials be used safely?
31 / Atomic structureBoth tiers
Answer: C Holding it with long tongs
To limit the dose, keep your distance (use tongs), keep the time short and use shielding. Lead absorbs radiation, so sources are kept in lead-lined boxes. The lead does not stop the source decaying; it only stops the radiation getting out.
Checked against Pearson Edexcel GCSE Physics 1PH0 specification, Topic 6 Radioactivity, 6.29 to 6.46P
32 / Atomic structureBoth tiers · separate only
Answer: C The one with the shorter half-life
Half-lives vary hugely between isotopes. With the same number of nuclei, a short half-life means many decays each second, so a high activity that soon dies away. A long half-life gives a lower activity that lasts for a very long time.
Checked against AQA GCSE Physics 8463 specification, 4.4.3.2 Different half-lives of radioactive isotopes
33 / Atomic structureBoth tiers · separate only
Answer: D Gamma passes out of the body to a detector
A tracer is put into the body to show how an organ is working. It should emit gamma, which leaves the body to reach a detector and ionises least. Its half-life must last long enough for the test but be short enough that it soon stops emitting.
Checked against AQA GCSE Physics 8463 specification, 4.4.3.3 Uses of nuclear radiation
34 / Atomic structureBoth tiers · separate only
Answer: C Gamma rays aimed at a tumour kill its cells
Radiation can control or destroy unwanted tissue such as a tumour. Gamma beams from outside, or a source placed inside the tumour, damage the cancer cells. Healthy cells nearby can be harmed too, so the dose is planned carefully. The patient does not become radioactive.
Checked against OCR Gateway Physics A J249 specification, P6.2c Uses and hazards
35 / Atomic structureBoth tiers · separate only
Answer: A A large nucleus splitting into two smaller nuclei
Nuclear fission is the splitting of a large, unstable nucleus such as uranium. Spontaneous fission is rare: usually the nucleus first absorbs a neutron, then splits into two smaller nuclei of roughly equal size.
Checked against AQA GCSE Physics 8463 specification, 4.4.4.1 Nuclear fission
36 / Atomic structureBoth tiers · separate only
Answer: B Neutrons, gamma rays and energy
When a nucleus splits it gives out two smaller nuclei, two or three neutrons and gamma rays, and releases energy. All the products move off with kinetic energy, and the gamma rays carry energy too.
Checked against AQA GCSE Physics 8463 specification, 4.4.4.1 Nuclear fission
37 / Atomic structureBoth tiers · separate only
Answer: D Neutrons from one fission cause more fissions
Each fission releases new neutrons, which can be absorbed by other nuclei and make them split too. In a reactor the chain reaction is controlled to control the energy released. In a nuclear weapon it is uncontrolled, causing an explosion.
Checked against AQA GCSE Physics 8463 specification, 4.4.4.1 Nuclear fission
38 / Atomic structureBoth tiers · separate only
Answer: A Two light nuclei joining to form a heavier nucleus
In nuclear fusion two light nuclei, such as hydrogen nuclei, join to form a heavier nucleus. The new nucleus has slightly less mass than the two before; that mass is converted into the energy of radiation. Fission is the opposite: a heavy nucleus splits.
Checked against AQA GCSE Physics 8463 specification, 4.4.4.2 Nuclear fusion
02 / Longer answersMarked by levels
Write your answer first, on paper. Then open it and tick off the points you made. How 6-mark questions are marked.
6 marks / How the model of the atom changedBoth tiers
At first, atoms were thought to be tiny solid spheres that could not be divided. When the electron was discovered, scientists knew atoms must contain smaller particles, so the plum pudding model was suggested: a ball of positive charge with negative electrons spread through it. Then, in the alpha particle scattering experiment, positively charged alpha particles were fired at a very thin sheet of gold foil. Most of the alpha particles went straight through, which showed that most of the atom is empty space. A few were deflected through large angles and a very small number bounced straight back, which showed that the positive charge and most of the mass must be concentrated in a tiny nucleus at the centre. The plum pudding model could not explain these results, so it was replaced by the nuclear model. Niels Bohr then suggested that the electrons orbit the nucleus at fixed distances, and his calculations agreed with experimental results. Later experiments showed that the positive charge of the nucleus is carried by protons, and James Chadwick showed that the nucleus also contains neutrons. Each time, the model changed because new evidence could not be explained by the old one.
Answers often describe the models but leave out the “why”. Link each change to its evidence: most alpha particles passing straight through shows empty space, and a few bouncing back shows a tiny, dense, positive nucleus.
6 marks / Contamination and irradiation comparedBoth tiers
A scientist works with a radioactive source that emits only alpha particles. One day she stands near the sealed source. On another day some of the radioactive material escapes as dust and she breathes some of it in.
On the first day the scientist is irradiated: she is exposed to radiation from a source that is outside her body. Irradiation does not make her radioactive, and it stops as soon as she moves away from the source. On the second day she is contaminated, because radioactive atoms are now inside her body, where they should not be. Contamination is more serious because it goes on: the radioactive atoms stay in her body and keep decaying, emitting radiation, until they are removed or have decayed. The type of radiation matters too. Alpha particles are very poorly penetrating and are stopped by a few centimetres of air or by the outer layer of the skin, so standing near a sealed alpha source is a low hazard, because almost none of the radiation reaches living cells. Inside her lungs, however, the alpha particles are absorbed by the cells around them. Alpha particles are strongly ionising, so they can damage these cells and cause mutations that may lead to cancer. So for this alpha source, the contamination on the second day is far more dangerous than the irradiation on the first.
Contamination and irradiation are often swapped. Irradiation is exposure to radiation from outside, and the person or object does not become radioactive; contamination means radioactive atoms are on or inside you, so the exposure continues.
6 marks / Nuclear fission and chain reactionsBoth tiers · separate only
For fission to happen, a uranium-235 nucleus must first absorb a neutron, which makes it unstable. The nucleus then splits into two smaller daughter nuclei of roughly equal size. At the same time it releases two or three neutrons and some gamma rays. A large amount of energy is released, and the daughter nuclei and neutrons move away quickly, so they have kinetic energy, which heats the surrounding material. The daughter nuclei are themselves radioactive. A chain reaction can happen because the neutrons released by one fission can be absorbed by other uranium-235 nuclei nearby, making those nuclei split too. Each of these fissions releases more neutrons, which can go on to cause even more fissions, so the number of fissions can grow very quickly. In a nuclear reactor the chain reaction is controlled, so that energy is released at a steady rate and can be used to generate electricity. In a nuclear weapon the chain reaction is uncontrolled, so a huge amount of energy is released almost at once, causing an explosion.
Fission and fusion are often confused. Fission is a large nucleus splitting after absorbing a neutron; write “nucleus”, not “atom”, and say that the new neutrons go on to cause further fissions.
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