atomic mass unit

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

Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005

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.

McGraw-Hill Concise Encyclopedia of Physics. © 2002 by The McGraw-Hill Companies, Inc.

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.

McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.