State laws of radioactive disintegration.

Explanation

1. Radioactivity is a spontaneous process.
2. During disintegration of an atom, either an `alpha`-particle or `beta`-particle is emitted.
3. The emission of an a-particle from an atom will change it, into a new atom whose charge number is reduced by two and mass number is reduced by four.
4. The emission of a `beta`-particle from an atom will change it, into a new atom whose charge number is raised by one, without any change in its mass number.
5. The number of atoms disintegrated per second at any instant is directly proportional to number of radioactive atoms actually present in sample at that instant.