atomic mass unit

American  

noun

Physics.

1. Also called dalton.  a unit of mass, equal to 1/12 (0.0833) the mass of the carbon-12 atom and used to express the mass of atomic and subatomic particles.

2. (formerly) a unit of mass, equal to 1/16 (0.0625) the mass of an oxygen atom having atomic mass 16. amu, AMU

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atomic mass unit British  

noun

1.  amu.  Also called: unified atomic mass unit.   dalton.  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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atomic mass unit Scientific  

1. A unit of mass equal to 1/12 the mass of an atom of the most common isotope of carbon (carbon 12), which is assigned a mass of 12 and has a value of 1.660 × 10 ^{- 24} grams. A hydrogen atom has a mass of 1 atomic mass unit since its mass is 1/12 the mass of carbon 12.

2. Also called dalton

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Etymology

Origin of atomic mass unit

First recorded in 1950–55

Example Sentences

Electrons are much smaller in mass than protons, weighing only 9.11 × 10-28 grams, or about 1/1800 of an atomic mass unit.

From Textbooks • Jun. 9, 2022