Isotope …, "m" are the atomic masses of each individual isotope, and "x", …, "x" are the relative abundances of these isotopes. Several applications exist that capitalize on properties of the various isotopes of a given element. Isotope separation is a significant technological challenge, particularly with heavy elements such as uranium or plutonium. Lighter elements such as lithium, carbon, nitrogen, and oxygen are commonly separated by gas diffusion of their compounds such as CO and NO. The separation of hydrogen and deuterium is unusual because it is based on chemical rather than physical properties, for example in the Girdler sulfide process.
Isotopes of curium Isotopes of curium Curium (Cm) is an artificial element with an atomic number of 96. Because it is an artificial element, a standard atomic weight cannot be given, and it has no stable isotopes. The first isotope synthesized was Cm in 1944, which has 146 neutrons. There are 21 known radioisotopes with atomic masses ranging from Cm to Cm. There are also four known nuclear isomers (Cm, Cm, Cm, and Cm). The longest-lived isotope is Cm, with a half-life of 15.6 million years – several orders of magnitude longer than the half-life of all known nuclei of elements beyond curium