Question #1cc3d

1 Answer
Aug 7, 2016

Answer:

"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.