Question

Why only alpha particles are emitted by radioactive nuclei while beta gamma rays not emmiting in rutherford model?

Answer 1

Radioactive nuclei emits three types of radiation:
Alpha particle
Beta particle
Gamma ray
The sole purpose of Radioactive decay is to lower down the energy of the nuclei. Since the binding energy of alpha particle(28.3 MeV) is very high, it will take away greater amount of energy than individual particles. Hence, it is energetically favourable for the nuclei to emit alpha particles instead of individual nucleons.