Relative atomic mass & Relative molecular mass

What is relative atomic mass?

All elements in the periodic table have two numbers next to them. The bigger one is the relative atomic mass (Ar) of the element. Because elements can exist as a different number of isotopes, when we talk about the element as a whole we use relative atomic mass rather than mass number.

What if an element has more than one isotope?

If an element has more than one isotope, its Ar is the average of all the mass numbers of all the different isotopes. If it has one isotope its Ar will be the same as its mass number.

What is relative formula mass?

Relative atomic masses can be used to find the relative formula mass of a compound.

How to find the relative formula mass (Mr) of a compound?

you add together the relative atomic mass values (Ar values) for all the atoms in its formula