Atomvikten

Atomvikten, or atomic weight, is the average mass of the atoms of an element as they occur in nature, weighted by the relative abundances of the element’s isotopes. It is defined in relation to carbon-12, so that the standard atomic weight reflects how heavy the element’s natural atoms are on average. In chemistry, the atomic mass of a single atom (or a specific isotope) is usually given in atomic mass units (amu), while the standard atomic weight represents a bulk property of naturally occurring material. The molar mass used in calculations in the laboratory is numerically equal to the standard atomic weight and is expressed in grams per mole (g/mol).

How it is determined: the standard atomic weight is calculated from the masses of an element’s isotopes and their natural abundances. For most elements, this yields a single representative value. However, for a few elements with variable isotopic composition in nature, the standard atomic weight may be reported as a range to reflect regional or geological differences.

Uses and distinctions: atomic weight differs from atomic mass: the former is an average for natural samples, while the latter refers to the mass of a particular atom or isotope. Atomic weight is a fundamental input in quantitative chemistry, enabling conversions between grams and moles, stoichiometric calculations, and comparisons of element properties within the periodic table.

Summary: atomvikten connects isotopic makeup to macroscopic chemical calculations, providing a standardized way to express the average mass of an element’s natural atoms. It is standardized by conventions used on periodic tables and in chemical literature.