The process of splitting an atom into two lighter atoms is called
a. nuclear disintegration.
b. nuclear separation.
c. nuclear fission.
d. nuclear fusion.

Answer is: C. nuclear fission.

Nuclear fission is a nuclear reaction or a radioactive decay where nucleus of atom split into smaller ligher nuclei.

Nuclear fission is exothermic reaction which release large amounts of energy (electromagnetic radiation or as kinetic energy, which heat reactors where fission reaction take place).

The process of splitting of an atom into two lighter atoms is called is called nuclear fission.

Explanation:

There are two types of nuclear decay reactions:

Hence, the process of splitting of an atom into two lighter atoms is called is called nuclear fission.