Answer
These variants are called isotopes. Because the like charges of the protons repel each other, these forces are always trying to push the atom's nucleus apart.
Explanation:
Elements having an atomic number greater than 83 are radioisotopes in nature.
These elements have unstable nuclei and are radioactive.
These variants are called isotopes. Because the like charges of the protons repel each other, these forces are always trying to push the atom's nucleus apart