7.6 describe the effects on the atomic and mass numbers of a nucleus of the emission of each of the three main types of radiation

An alpha particle is made up of 2 protons and 2 neutrons, therefore, when an alpha particle is emitted, the proton number will decrease by 2 (as 2 protons have been released) and the mass number will decrease by 4 (as 4 nucleons will have been released).

A beta particle is comprised of one electron, this means that when a beta particle is emitted, the atomic number will increase by one.

There is no effect on an atoms atomic or mass numbers if a gamma ray is emitted. This is because it is comprised of energy, not protons/neutrons/electrons.