Isotopes

Isotopes are variants of a specific chemical element which differ in neutron number. All isotopes of a given element have the same number of protons, but different numbers of neutrons in each atom, resulting in each isotope having a different number of nucleons. An isotope's symbol can be written as seen in the picture on the right, where A=the number of nucleons (protons+nucleons), Z= the number of protons, and X=the element symbol. The number of protons is equal to the atomic number, which is equal to the number of electrons in a neutral atom.

Do differ different isotopes of the same element from each other, we specify the amount of nucleons as a part of the element's name. For example, carbon-12, carbon-13 and carbon-14.

Isotope vs nuclide
This can easily become a little bit complicated, but to explain this in a basic sense; Isotopes are an under category of nuclide. Nuclide is the common name for all pairings of protons and neutrons.