Every chemical element has a unique atomic number (Z) that represents the number of protons in its nucleus. Most elements have contrasting quantities of neutrons among various atoms, with these variations being alluded to as isotopes. For instance, carbon has three normally happening isotopes: the majority of its particles have six protons and most have six neutrons also, however around one percent have seven neutrons, and an extremely little portion has eight neutrons. Isotopes are never isolated in the periodic table; they are constantly gathered together under a solitary element. Elements with no steady isotopes have the atomic masses of their most steady isotopes, where such masses are displayed, in parentheses.