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atomic weight
6 dictionary results for: Atomic weight
Dictionary.com Unabridged (v 1.1) - Cite This Source - Share This
atomic weight
–noun Chemistry.
the average weight of an atom of an element, formerly based on the weight of one hydrogen atom taken as a unit or on 1/16 the weight of an oxygen atom, but after 1961 based on 1/12 the weight of the carbon-12 atom. Abbreviation: at. wt.

[Origin: 1820–30]
American Heritage Dictionary - Cite This Source - Share This
atomic weight  
n.   The average mass of an atom of an element, usually expressed relative to the mass of carbon 12, which is assigned 12 atomic mass units.

WordNet - Cite This Source - Share This
atomic weight

noun
(chemistry) the mass of an atom of a chemical element expressed in atomic mass units [syn: atomic mass

The American Heritage Science Dictionary - Cite This Source - Share This
atomic weight  
The mass of an atom expressed in atomic mass units. The atomic weight of an element having more than one principal isotope is calculated both from the atomic masses of the isotopes and from the relative abundance of each isotope in nature. For example, the atomic weight of the element chlorine is 35.453, determined by averaging the atomic masses and relative abundances of its two main naturally occurring isotopes, which have atomic masses of about 35 and 37. Also called relative atomic mass. Compare atomic mass. See also mass number.

American Heritage New Dictionary of Cultural Literacy, Third Edition - Cite This Source - Share This
atomic weight

The mass of a given atom, measured on a scale in which the hydrogen atom has the weight of one. Because most of the mass in an atom is in the nucleus, and each proton and neutron has an atomic weight near one, the atomic weight is very nearly equal to the number of protons and neutrons in the nucleus. (See atomic number.)


American Heritage Stedman's Medical Dictionary - Cite This Source - Share This

atomic weight n.
Abbr. at wt, AW
The average mass of an atom of an element, usually expressed relative to the atomic mass of carbon 12.

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