Atomic mass unit
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The atomic mass unit (symbol: u), also called the dalton (symbol: Da), is a unit of mass used with the SI. The value of the atomic mass unit is a physical constant called the atomic mass constant (symbol: mu): the 2006 CODATA recommended value is 1.660 538 782(83) × 10−27 kg.[1]
Definition and measurement
The atomic mass constant is defined as one twelfth of the rest mass of an isolated atom of carbon-12 in its nuclear and electronic ground state.[2] An equivalent definition used to determine to value of the atomic mass constant is the molar mass constant divided by the Avogadro constant.
- mu = Mu/NA
As the molar mass constant has a defined value in the International System of Units, the atomic mass constant is determined by the Avogadro constant.
References
- ↑ Mohr, Peter J.; Taylor, Barry N.; Newell, David B. CODATA Recommended Values of the Fundamental Physical Constants: 2006. Rev. Mod. Phys. 2008, 80 (2), 633–730. doi:10.1103/RevModPhys.80.633, <http://physics.nist.gov/cuu/Constants/codata.pdf>. Direct link to value.
- ↑ atomic mass constant, <http://goldbook.iupac.org/A00497.html> (accessed 16 July 2010), Compendium of Chemical Terminology Internet edition; International Union of Pure and Applied Chemistry (IUPAC).
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