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.

Beta is an electron (or positron). Gamma is an electromagnetic wave and not a particle. For alpha decay it is likely you will be given a starting atom such as radon: \(_{86}^{219}\textrm{Rn}\) ...

In beta decay, a proton or neutron in a nucleus emits a beta particle (an electron or its anti-particle, a positron ... the emitted beta particle and two alpha particles with high precision.