Soddy and Rutherford, from their experimental study regarding the radioactive disintegration formulated the following laws, known as laws of radioactive disintegration.
1. Radioactivity is a spontaneous process which does not depend upon external factors like temperature, pressure etc. i.e. a radioactive element is in a state of disintegration which depends upon law of chance. It means it is impossible to predict which particular atom of the radioactive element will disintegrate in a given time interval.
2. During disintegration of an atom, either an particle or a ß particle is emitted. Both of these particles are never emitted simultaneously. Also at a time, an atom will not emit more than one ß particle.
3. The emission of 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 ß particle from an atom is raised by one, without any change in its mass number.
5. The number of atoms disintegrated per second (i.e. rate of disintegration of radioactive atoms) at any instant is directly proportional to the number of radioactive atoms actually present in the sample at that instant. This is also known as radioactive decay law.