Question #1cc3d

1 Answer
Ernest Z.
Aug 7, 2016

"They" defined the unified atomic mass unit (u) as exactly ¹/₁₂ the mass of a carbon-12 atom.

Explanation:

"They" knew quite precisely what the mass of a carbon-12 atom was, so it was easy to calculate that it took #6.02 × 10^23# atoms of carbon-12 to have a mass of 12 g.

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