Mass

• Relative atomic mass is the weighted average mass of an element compared to 1/12 of the mass of an atom of carbon-12
• Relative molecular mass is the average mass of one molecule of a compound compared to 1/12 of the mass of one atom of carbon-12
• Relative isotopic mass is the mass of an atom of an isotope compared to 1/12 of the mass of one atom of carbon-12