Relative Masses
- Relative atomic mass has the symbol Ar
- This is the average mass of the atoms of an element measured relative to the mass of one atom of carbon-12
- This is calculated from the mass number and relative abundances of all the isotopes of a particular element
- Relative molecular mass is the average mass of the atoms of one molecule of an element or compound measured relative to the mass of one atom of carbon-12
- Relative formula mass has the symbol Mr and it refers to the total mass of the molecule
- To calculate the Mr of a substance, you have to add up the relative atomic masses of all the atoms present in the formula
