AQA · GCSE · Physics
Course version: 8463 · Version from Sept 2016
Nuclear equations are used to represent radioactive decay.
Full specification wording
Nuclear equations: Nuclear equations are used to represent radioactive decay.
A nuclear equation shows what a nucleus turns into when it decays.
Checked against the AQA 8463 specification (opens in a new tab) on .
- Point 1 of 6
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
A nuclear equation shows what a nucleus turns into when it decays. The original nucleus goes on the left, and the new nucleus plus the emitted particle go on the right, joined by an arrow. Each nucleus is written with its mass number above and its atomic number below the chemical symbol, as in ²³⁸₉₂U. Two conservation rules govern the equation: the total mass number on the right equals the mass number on the left, and the total atomic number on the right equals the atomic number on the left, because nucleon number and charge are both conserved. Those two running totals are all you need to complete any equation the exam sets.
What earns the marks
- Writing the original nucleus on the left and the new nucleus plus emitted particle on the right.
- Using the nuclide notation with mass number above the atomic number.
- Stating that the total mass number is the same on both sides.
- Stating that the total atomic number, and so the charge, is the same on both sides.
Common mistakes and how to put them right
Writing the emitted particle on the same side as the original nucleus.
Swapping the positions of the mass number and the atomic number.
Balancing the mass numbers and leaving the atomic numbers unbalanced.
Adding state symbols as though it were a chemical equation.
Exam tips
- Write the two totals in the margin, one for mass numbers and one for atomic numbers, before filling any gaps.
- Check both totals at the end; each is usually worth a separate mark.
- Keep the arrow pointing from the original nucleus to the products, never the other way.
Try the lesson
The start of the Nuclear equations: Nuclear equations are used to represent radioactive decay. lesson, made from checked teaching notes for this specification point.
Have a go first
Which quantity is always the same on both sides of a balanced nuclear equation?
Listen
A nuclear equation shows what a nucleus turns into when it decays. The original nucleus goes on the left, and the new nucleus plus the emitted particle go on the right, joined by an arrow. Each nucleus is written with its mass number above and its atomic number below the chemical symbol, as in ²³⁸₉₂U. Two conservation rules govern the equation: the total mass number on the right equals the mass number on the left, and the total atomic number on the right equals the atomic number on the left, because nucleon number and charge are both conserved. Those two running totals are all you need to complete any equation the exam sets. A strong answer earns marks for these points. writing the original nucleus on the left and the new nucleus plus emitted particle on the right. using the nuclide notation with mass number above the atomic number. stating that the total mass number is the same on both sides. stating that the total atomic number, and so the charge, is the same on both sides. Exam tip: Write the two totals in the margin, one for mass numbers and one for atomic numbers, before filling any gaps.
See it
Key words
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nuclear equations
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nuclide notation
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conservation of mass number
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conservation of charge
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See every definition
- nuclear equations
- Used to represent radioactive decay, showing what a nucleus turns into when it decays.
- nuclide notation
- Each nucleus is written with its mass number above and its atomic number below the chemical symbol.
- conservation of mass number
- The total mass number on the right equals the mass number on the left, because nucleon number is conserved.
- conservation of charge
- The total atomic number on the right equals the atomic number on the left, because charge is conserved.
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
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