Concept of isotopes:
It can be defined as the atoms of the same element, having the same atomic number but different mass numbers. Therefore, we can say that there are three isotopes of a hydrogen atom, namely protium, deuterium and tritium.
Applications of Isotopes:
An isotope of iodine is used in the treatment of goitre.
An isotope of uranium is used as a fuel in nuclear reactors.
An isotope of cobalt is used in the treatment of cancer.