Structure of the proton
Nuclei are made up of two similar components: the proton and the neutron. The positive electrical charge of the proton is equal and opposite to the negative charge on the electron. This charge, sometimes called ‘e’, is known as the ‘elementary’ charge. The proton is a very small particle with a radius of under a millionth of a billionth of a metre. Despite its size, the proton is a highly complex particle made up of even smaller particles: quarks. For all phenomena linked to radioactivity, however, this higher level of complexity can be safely ignored.