ABSTRACT
Before looking at the mathematics of decay, it is important to remember the difference between atomic mass and average atomic mass. Atomic mass is the mass of a single atom, and it is numerically equivalent to the mass of 1 mole of atoms. Atomic mass is expressed in unified atomic mass units (u). When we are talking about a mole of atoms, the units are grams per mole (g/mol). For example, the mass of a single 12C atom is 12.00 u, while the mass of a whole mole (6.022 × 1023) of 12C atoms would be 12.00 g. The unified atomic mass unit is more convenient when referring to the mass of single atoms and is more commonly used in nuclear science. To convert one to the other, one unified atomic mass unit is equal to 1.66054 × 10−24 g.
