AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
Radioactive decay and nuclear radiation: a neutron (n).
A neutron is a neutral subatomic particle found in the nucleus of an atom.
Checked against the AQA 8464 specification (opens in a new tab) on .
- Point 9 of 10
Study notes
From the checked teaching notes for this specification point.
The idea
A neutron is a neutral subatomic particle found in the nucleus of an atom. It has a relative mass of 1 and no electric charge, so it is written as n in nuclear equations. As well as alpha, beta, and gamma radiation, a neutron can be emitted from an unstable nucleus as a form of radioactive decay. Because a neutron has no charge, it is not deflected by electric or magnetic fields and can penetrate deeply into materials. In a nuclear equation, a neutron is shown with a mass number of 1 and an atomic number of 0, for example ¹₀n. The number of neutrons in a nucleus is found by subtracting the atomic number from the mass number.
For example: Carbon-12 has 6 protons and 6 neutrons because 12 − 6 = 6.
What earns the marks
- A neutron is a subatomic particle found in the nucleus of an atom.
- A neutron has a relative mass of 1 and no electric charge, so it is neutral.
- In nuclear equations, a neutron is represented by the symbol n with a mass number of 1 and an atomic number of 0, for example ¹₀n.
- The number of neutrons in a nucleus equals the mass number minus the atomic number.
- A neutron can be emitted from an unstable nucleus as a type of radioactive decay.
- Because neutrons have no charge, they are not deflected by electric or magnetic fields and are highly penetrating.
Common mistakes and how to put them right
Confusing neutrons with protons.
Put it right: Check the charge and position in the nucleus.
Thinking neutrons are not emitted during radioactive decay.
Put it right: Unstable nuclei can emit neutrons to become more stable.
Forgetting that a neutron has a mass number of 1 and atomic number of 0 in equations.
Put it right: Write ¹₀n and balance mass and atomic numbers.
Exam tips
- Use the formula number of neutrons = mass number − atomic number when asked to find neutron numbers.
- In nuclear equations, write a neutron as ¹₀n and check that mass and atomic numbers balance.
- Remember that neutron emission is a form of radioactive decay, alongside alpha, beta, and gamma.
Try the lesson
The start of the Radioactive decay and nuclear radiation: a neutron (n). lesson, made from checked teaching notes for this specification point.
Have a go first
Which particle emitted during radioactive decay is a neutron?
Listen
A neutron is a neutral subatomic particle found in the nucleus of an atom. It has a relative mass of 1 and no electric charge, so it is written as n in nuclear equations. As well as alpha, beta, and gamma radiation, a neutron can be emitted from an unstable nucleus as a form of radioactive decay. Because a neutron has no charge, it is not deflected by electric or magnetic fields and can penetrate deeply into materials. In a nuclear equation, a neutron is shown with a mass number of 1 and an atomic number of 0, for example ¹₀n. The number of neutrons in a nucleus is found by subtracting the atomic number from the mass number. For example, carbon-12 has 6 protons and 6 neutrons because 12 − 6 = 6. A strong answer earns marks for these points. A neutron is a subatomic particle found in the nucleus of an atom. A neutron has a relative mass of 1 and no electric charge, so it is neutral. In nuclear equations, a neutron is represented by the symbol n with a mass number of 1 and an atomic number of 0, for example ¹₀n. The number of neutrons in a nucleus equals the mass number minus the atomic number. A common slip: Confusing neutrons with protons: neutrons have no charge, while protons are positively charged. Instead, check the charge and position in the nucleus. Exam tip: Use the formula number of neutrons = mass number − atomic number when asked to find neutron numbers.
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