What is the unit typically used to express atomic mass?

The unit typically used to express atomic mass is atomic mass units (amu). This unit is specifically designed to provide a convenient scale for comparing the masses of atoms and molecules. One atomic mass unit is defined as one twelfth of the mass of a carbon-12 atom, which establishes a standard for measuring atomic masses. This allows chemists and scientists to quantify the mass of individual atoms and compare them easily, as atomic masses are often very small numbers when expressed in grams or kilograms.

Using grams or kilograms to express atomic mass would result in impractically small decimal values, making comparisons less intuitive. Moles, on the other hand, are used to measure the amount of substance rather than mass, thus they are not suitable for expressing atomic mass directly. Therefore, atomic mass units provide a clear and precise way to express and compare the masses of different atomic species.