The correct options are as follows:
17. C.
Radioactive decay refers to the process by which an unstable atomic nucleus loses energy by giving out radiations. The radiations emit can be in form of alpha or beta particles or gamma rays. Radioactive decay is a random process, that is, one can not predict when it would happen. Radioactive decay occurs when the nucleus of an atom decay and no longer have enough binding energy to hold the atomic sub particles together.
18. B.
Radioactive decay occurs when the nucleus no longer have enough energy to hold the sub particles in the nucleus together. This situation always occur when there are excess protons or neutrons in the nucleus of the atom. In the nucleus of an atom, two forces are usually at work, nuclear and electrostatic forces. While proton experience both of these forces, neutron only experience the nuclear force. These two forces that are in opposition bring about radioactive decay.
