The atomic masses for elements are the same as the atomic number. relative masses determined by comparison with a standard reference. unknown. actual masses determined by weighing individual atoms.

Relative masses determined by comparison with a standard reference.

Explanation:

Atomic mass (Also called Atomic Weight, although this denomination is incorrect, since the mass is property of the body and the weight depends on the gravity) Mass of an atom corresponding to a certain chemical element). The uma (u) is usually used as a unit of measure. Where u. m. a are acronyms that mean "unit of atomic mass".

It is equivalent to one twelfth of the mass of the nucleus of the most abundant isotope of carbon, carbon-12. It corresponds roughly to the mass of a proton (or a hydrogen atom). It is abbreviated as "uma", although it can also be found by its English acronym "amu" (Atomic Mass Unit). However, the recommended symbol is simply "u".

The atomic masses of the chemical elements are usually calculated with the weighted average of the masses of the different isotopes of each element taking into account the relative abundance of each of them, which explains the non-correspondence between the atomic mass in umas, of an element, and the number of nucleons that harbors the nucleus of its most common isotope.