Atomic Weight

Name:
Atomic Weight
Detailed information:
(aw). The average weight or mass of all the isotopes of an element as determined from the proportions in which they are present in a given element, compared with the mass of the 12 isotope of carbon (taken as precisely 12.000), which is the official international standard. The true atomic weight of carbon when the masses of its isotopes are averaged is 12.01115; that of oxygen is 15.9994. The total mass of any atom is the sum of the masses of all its constituents (protons, neutrons, and electrons). Official atomic weight determinations are released periodically by the IUPAC.See Atomic Number; Mass Number.