atomic mass

[ uh-tom-ik mas ]

noun

, Chemistry.

1. the mass of an isotope of an element measured in units formerly based on the mass of one hydrogen atom taken as a unit or on 1/16 (0.0625) the mass of one oxygen atom, but after 1961 based on 1/12 (0.0833) the mass of the carbon-12 atom.

atomic mass

noun

1. the mass of an isotope of an element in atomic mass units
2. short for relative atomic mass See atomic weight

atomic mass

1. The mass of a given atom or molecule, expressed in atomic mass units.
2. Compare atomic weightSee also mass number

Word History and Origins

Origin of atomic mass¹

First recorded in 1895–1900

Example Sentences

"Many thousands of atomic nuclei that have yet to be measured may exist in nature," said Matthew Mumpower, a theoretical physicist and co-author on several recent papers detailing atomic masses research.

From Science Daily

When we refer to light or heavy elements, we're talking about their atomic mass.

From Science Daily

Wallner is particularly interested in the radioactive iron isotope with the atomic mass of 60.

From Science Daily

Twelve, named for the atomic mass of carbon, has developed a process to make jet fuel using renewable electricity, water and waste biomass CO2 instead of fossil fuels.

From Seattle Times

A silvery, alkaline earth metal called strontium comes in different versions, or isotopes, each with a different atomic mass.

From Scientific American