What unit of mass is designated as one-sixteenth the mass of oxygen-16?

The atomic mass unit, or amu, is defined as one twelfth of the mass of a carbon-12 atom. However, when specifically looking at the mass of oxygen-16, the atomic mass unit is also directly expressed as one-sixteenth of that isotope's mass. This unit is fundamental in atomic and molecular physics, allowing scientists to express the masses of atoms and molecules relative to one another.

In contrast, the gram is a standard unit of mass in the metric system, but it does not directly relate to atomic-scale measurements without converting between units. The mole is a quantity that represents a specific number of particles, usually atoms or molecules, rather than a measurement of mass. The dalton is a similar unit used in biochemistry, which is synonymous with the atomic mass unit. Thus, while other choices might seem relevant, the atomic mass unit uniquely fits the description by linking specifically to the mass of oxygen-16 in a clear and direct manner.