Answer:
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.