Isotope

An element of different molecular mass. A form of an element of a specific atomic mass. The number of neutrons varies between isotopes. Like this some elements have different atomic masses.

“carbon-12 has six protons and six neutrons, whereas carbon-14 has 6 protons and 8 neutrons. These are different isotopes of the same element”.
“Note: In The Simpsons, the Springfield baseball team is called The Springfield Isotopes. Echoing Homer's job in the nuclear power plant”.