When the nuclei of two atoms come together to make a bigger nucleus.
References
Edexcel
- Fuses, page 193, GCSE Combined Science; The Revision Guide, CGP, Edexcel
- Fuses, page 80, GCSE Physics; The Revision Guide, CGP, Edexcel
- Fuses, pages 247, 248, GCSE Physics, CGP, Edexcel