GCSE Physics

Beta Decay Example

Tritium is radioactive and decays by emitting a beta particle. Let us work out what it decays into:

Firstly, X must have the same mass number (3) since beta particles have virtually no mass compared to nucleons. The mass before is the same as after.

Secondly, the charge after must be the same as before. We have 1 proton on the left (1+ charge) and, so far, 1 electron on the right (1- charge). So:

+1 = (charge of X) + (-1)

The charge of X must be +2, giving:

So Tritium decays into Helium-3, which is not radioactive.

GCSE PhysicsRadioactivity Menu GCSE PhysicsGo to next page