atomic mass unit


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Related to atomic mass unit: relative atomic mass, atomic weight

atomic mass unit

or

amu,

in chemistry and physics, unit defined as exactly 1-12 the mass of an atom of carbon-12, the isotopeisotope
, in chemistry and physics, one of two or more atoms having the same atomic number but differing in atomic weight and mass number. The concept of isotope was introduced by F.
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 of carbon with six protons and six neutrons in its nucleus. One amu is equal to approximately 1.66 × 10−24 grams.

Atomic mass unit

An arbitrarily defined unit in terms of which the masses of individual atoms are expressed. One atomic mass unit is defined as exactly of the mass of an atom of the nuclide 12C, the predominant isotope of carbon. The unit, also known as the dalton, is often abbreviated amu, and is designated by the symbol u. The relative atomic mass of a chemical element is the average mass of its atoms expressed in atomic mass units.

atomic mass unit

[ə′täm·ik ′mas ′yü·nət]
(physics)
An arbitrarily defined unit in terms of which the masses of individual atoms are expressed; the standard is the unit of mass equal to one-twelfth the mass of the carbon atom, having as nucleus the isotope with mass number 12. Abbreviated amu. Also known as dalton.

atomic mass unit

a unit of mass used to express atomic and molecular weights that is equal to one twelfth of the mass of an atom of carbon-12. It is equivalent to 1.66 × 10--27 kg
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Castleman's mass spectrometer could not register anything larger than 1,200 atomic mass units,k but he and others hope they will one day discover that met-cars come in a variety of sizes, just as fullerenes do.
Fortunately, the SSIMS spectrum for dimethyl silicone has strong peaks at 73 and 147 atomic mass units (AMU) from ([CH.
Furthermore, the weights of different elements will not accord exactly with the number of atomic mass units they possess.