atomic weight


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Related to atomic weight: molecular weight

weight

 [wāt]
1. heaviness; the degree to which a body is drawn toward the earth by gravity. (See also Tables of Weights and Measures in the Appendix.) Abbreviated wt.
2. in statistics, the process of assigning greater importance to some observations than to others, or a mathematical factor used to apply such a process.
apothecaries' weight see apothecaries' system.
atomic weight the sum of the masses of the constituents of an atom, expressed in atomic mass units (or daltons), in SI units (i.e., kilograms), or as a dimensionless ratio derived by comparing the mass to the mass of an atom of carbon-12, which is taken as 12.000. Abbreviated At wt.
avoirdupois weight see avoirdupois system.
equivalent weight the amount of substance that combines with or displaces 8.0 g of oxygen (or 1.008 g of hydrogen), usually expressed in grams; for acid/base reactions, one equivalent donates or receives a mole of protons and the equivalent weight is the ratio of the molecular weight to the number of protons involved in the reaction. For oxidation-reduction reactions, one equivalent donates or receives a mole of electrons and the equivalent weight is the ratio of the molecular weight to the number of electrons involved in the reaction.
gram molecular weight the molecular weight of a substance expressed in grams; one gram molecular weight of a molecular substance contains one mole of molecules. See also mole1.
low birth weight (LBW) see under infant.
molecular weight the weight of a molecule of a chemical compound as compared with the weight of an atom of carbon-12; it is equal to the sum of the weights of its constituent atoms and is dimensionless. Abbreviated Mol wt or MW. Although widely used, the term is not technically correct; relative molecular mass is preferable.
very low birth weight (VLBW) see under infant.

a·tom·ic weight (at. wt., AW),

the mass in grams of 1 mol (6.02 × 1023 atoms) of an atomic species; the mass of an atom of a chemical element in relation to the mass of an atom of carbon-12 (12C), which is set equal to 12.000, thus a ratio and therefore dimensionless (although the actual mass, numerically the same, is sometimes expressed in daltons); not necessarily the weight of any individual atom of an element, since most elements are made up of several isotopes of different masses; for example, the atomic weight of chlorine is 35.4527, because it is composed of 35Cl and 37Cl in proportions that give an average of 35.4527.
See also: molecular weight.

a·tom·ic weight

(AW, at. wt.) (ă-tom'ik wāt)
The mass in grams of 1 mol (6.02 × 1023, atoms) of an atomic species; the mass of an atom of a chemical element in relation to the mass of an atom of carbon 12 (12C), which is set equal to 12.000, thus a ratio and therefore dimensionless (although the actual mass, numerically the same, is sometimes expressed in daltons); not necessarily the weight of any individual atom of an element, because most elements are made up of several isotopes of different masses.
See also: molecular weight

atomic weight

the weight of an atom of an element in relation to hydrogen, which is considered as one.

a·tom·ic weight

(AW, at. wt.) (ă-tom'ik wāt)
The mass in grams of 1 mol (6.02 × 1023, atoms) of an atomic species.
See also: molecular weight
References in periodicals archive ?
Several chemists had already drawn up charts that arrayed the elements in horizontal and vertical rows according to atomic weights. Indeed, the chemist Lothar Meyer had constructed a table much like Mendeleev's, but unfortunately had not published it.
The numerical value of the phase shift p is initially unknown and must be adjusted in such a way that the largest possible amount of atomic weights can be expressed through a continued fraction.
Until such time as more was known about molecular makeup, the values obtained for atomic weights would be dubious.
It is necessary to note that the dates published in the table of "Experience of Systems of Elements Founded on Their Atomic Weights and Chemical Similarity" permits us to use them in order to prove the correctness of Mendeleev's work.
The difference between this expression and mass fraction is the substitution of atomic number for atomic weight.
These adjustments may seem trivial, but they reflect a valuable recognition of the importance of atomic weight in chemistry--and reveal some of the nuances hiding within Feynman's concise sentence.--Tom Siegfried, Editor in Chief
For nuclei with atomic weight below 40, the numbers of protons and neutrons are approximately identical.
Just as the weight listed on your driver's license doesn't necessarily reflect your actual poundage, the official atomic weights of most chemical elements are actually more like ballpark estimates than precise constants.
Berzelius (see 1803) was one of those who labored to determine atomic weights, and no one in his time was as careful as he.
We are pleased to support the recognition of the first-ever National Hydrogen and Fuel Cell Day on October 8, aptly chosen to represent the atomic weight of hydrogen (1.008).
Atomic weight refers to the averaged mass of the atoms of a chemical element using a scale based on a standard atomic nucleus.
He also made an accurate determination of the atomic weight of chlorine.