Definitions

Question 1

Relative isotopic mass

Answer 1

Mass of an atom of an isotope compared with 1/12 mass of carbon 12

Question 2

Relative atomic mass

Answer 2

Weighted mean mass of an atom of an element compared with 1/12 of the mass of an atom of carbon -12

Question 3

Relative molecular mass

Answer 3

Weighted mean mass of a molecule compared with 1/12 of the mass of an atom of carbon -12 (only applies to simple covalent molecules e.g O2)
- Add up mass numbs

Question 4

Relative formula mass -RFM

Answer 4

Weighted mean mass of a formula unit compared to 1/12th of the mass of an atom of carbon -12