Radioisotopes are unstable forms of isotopes because they contain an excess number of . radioisotopes lose nuclear energy as they decay or break down, thus becoming stable. the half-life is the amount of time it takes for 50% of the radioisotope to become stable. the amount of time it takes for 50% of radioactive material to leave the body is referred to as the half-life.

neutrons, more, physical, biological

Explanation:

Radioisotopes are those isotopes of an atom which due to excessive energies are unstable, this unstability results from combination of protons and neutrons which are unstable.

Thus to achieve stability, these isotopes loses their energy when they decay or disintegrate.

The time taken by the radioisotope to achieve about 50% stability after disintegration is known as Physical half-life.

The biological half-life refer to the time taken by the radioisotope for the elimination of about 50% of the radioactive substance.