Atomic mass unit
Atomic mass unit
The Atomic mass unit (AMU), also known as the Dalton (symbol: Da), is a standard unit of mass that quantifies mass on an atomic or molecular scale (atomic mass).
Pronunciation
- Atomic mass unit: /əˈtɒmɪk mæs ˈjuːnɪt/
- Dalton: /ˈdɔːltən/
Etymology
The term "Atomic mass unit" is derived from the method used to calculate the masses of atoms on a scale relative to hydrogen (or one twelfth of the mass of carbon-12), while "Dalton" is named after the English scientist John Dalton, who proposed the atomic theory.
Definition
One atomic mass unit is defined as exactly 1/12 of the mass of a carbon-12 atom, which is approximately 1.66053906660(50)×10−27 kg.
Related Terms
- Atomic mass: The mass of an atom, most often expressed in unified atomic mass units.
- Mole (unit): The unit of measurement in the International System of Units (SI) for amount of substance.
- Avogadro's number: The number of constituent particles, usually atoms or molecules, in one mole of a given substance.
- Isotope: Each of two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei.
See Also
External links
- Medical encyclopedia article on Atomic mass unit
- Wikipedia's article - Atomic mass unit
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