Nuclear equations — AQA GCSE Physics
Test yourself on Nuclear equations with AQA GCSE practice questions.
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Nuclear equations explained
A nuclear equation shows what a nucleus turns into when it decays.
Read the full explanation
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.
Your focus
- Write a nuclear equation with the original nucleus, the new nucleus and the emitted particle in the correct positions.
- State the two quantities that must balance on both sides of a nuclear equation.
- Check a given nuclear equation and say whether it balances, explaining any error.
Nuclear equations exam tips
Marking Points
- one mark for writing the original nucleus on the left and the new nucleus plus emitted particle on the right
- one mark for using the nuclide notation with mass number above the atomic number
- one mark for stating that the total mass number is the same on both sides
- one mark for stating that the total atomic number, and so the charge, is the same on both sides
Examiner 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.
Common Mistakes
- 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