What is atomic mass?
Atomic mass
{'answer_start': array([21]), 'answer_text': array(['is the mass of an atom'], dtype=object)}
The atomic mass (ma) is the mass of an atom. Its unit is the unified atomic mass units (abbr. u) where 1 unified atomic mass unit is defined as ​1⁄12 of the mass of a single carbon-12 atom, at rest.[1] For atoms, the protons and neutrons of the nucleus account for nearly all of the total mass, and the atomic mass measured in u has nearly the same value as the mass number.