What is an Isotope?

These are atoms of the same element that contain different numbers of neutrons in their nucleus and the same number of protons. Most elements are made up of two or more natural isotopes; for example, tin (Sn) is made up of a mixture of 10 different isotopes, while only 21 of the 90 elements found in nature are made up of a single type of atom, including beryllium (Be) and sodium (Na).

Video about an Isotope