molecular mass — the total mass of all the atoms in a molecule. The mass of
each atom is simply its total number of protons and neutrons in the atom. Thus, the molecular
mass of a molecule is the total number of protons and neutrons in all the atoms in that
molecule. Obviously, the more atoms there are in a molecule, the higher its molecular mass
will be.
A water molecule has a molecular mass of 18. An
acetylsalicylic acid molecule has a
molecular mass of 182. Macromolecules
such as proteins have molecular masses
in the thousands or even hundreds of thousands.