# How do you represent the nucleus using isotopic notation?

The mass number of an element is the total number of protons and neutrons in the nucleus of a particular isotope of that element. Isotopic notation involves writing the mass number (which represents the nucleus) of the isotope as a superscript in front of the chemical symbol of the element. For example, all hydrogen atoms have one proton, but there are three isotopes due to the absence of or presence of neutrons. Hydrogen-1 (also called Protium) has one proton and no neutrons, so its mass number is 1. Hydrogen-2 (also called Deuterium), has one proton and one neutron, and its mass number is 2. Hydrogen-3 (also called tritium) has one proton and two neutrons, which gives it a mass number of 3. To represent each hydrogen isotope in isotopic notation, you would write "^1H for Protium, "^2H for Deuterium, and "^3H for Tritium.