After emitting an alpha or beta particle, the nucleus will often still be ‘excited’ and will need to lose energy. It does this by emitting a high energy electromagnetic wave called a gamma ray. Gamma ...

However, as the number of protons increases, more neutrons are needed to keep the nucleus stable. For example lead (lead-206) has 82 protons and has 124 neutrons. If the nucleus has too few neutrons, ...