Question

How can we use relative masses to compare elements?

Answer 1

Relative atomic mass (symbol: Ar) or atomic weight is a dimensionless physical quantitydefined as the ratio of the average mass of atoms of a chemical element in a given sample to one unified atomic mass unit. The unified atomic mass unit (symbol: u or Da) is defined as being ​1⁄12 of the atomic mass of a carbon-12 atom.[1][2] Since both values in the ratio are expressed in the same unit (u), the resulting value is dimensionless; hence the value is said to be relative.