What are isotopes?

Isotopes are a variant of a particular chemical element in the Periodic Table. They have the same atomic number, therefore the same number of protons and electrons. However they have a different number of neutrons meaning a different atomic mass. An example being Hydrogen which can exists as 3 different isotopes and these are; Protium with an atomic mass of 1, Deuterium with an atomic mass of 2 and lastly Tritium which has an atomic mass of 3. All these isotopes of Hydrogen have the same number of protons which is only 1. Protium has no neutrons whereas Deuterium has 1 neutron and and Tritium has 2 neutrons as they have different atomic mass numbers. This can be solved using a simple equation to work out the number of neutrons: ( atomic mass number - atomic number = number of Neutrons )The most common isotope of an element is the most stable and is what is indicated in the Periodic Table.