Standard atomic weight real life substances—for example, in pharmaceuticals and scientific research. Atomic weights are specific to single sources and samples of an element, such as the atomic weight of carbon in a particular bone from a particular archeological site. Standard atomic weight generalizes such values to the "range of atomic weights" which a chemist might expect to derive from many random samples from Earth. This range is the cause of the "interval notation" in some standard atomic weight values. Out of the 118 known chemical elements, 84 are stable and have this Earth-environment based value. Typically, such a value is, for example
Isotopes of flerovium Isotopes of flerovium Flerovium (Fl) is a synthetic element, and thus a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first isotope to be synthesized was Fl in 1999 (or possibly 1998). Flerovium has seven known isotopes, and possibly 2 nuclear isomers. The longest-lived isotope is Fl with a half-life of 1.9 seconds, but the unconfirmed Fl may have a longer half-life of 19 seconds. The below table contains various combinations of targets and projectiles which could be used to form compound nuclei with an atomic number of 114. "This section deals