# What is the unit mass of an atom on the periodic table?

The atomic weight or relative atomic mass does not really have units, but scientists have given them units, such as the atomic mass unit, amu; unified atomic mass unit, u; or the Dalton, Da, as an alternative symbol for the unified atomic mass unit. One u is $\frac{1}{12}$ the mass, $m$, of a $\text{^12""_6"C atom}$, the most abundant carbon isotope.