Calculating relative atomic mass for elements - Higher tier
Most elements contain a mixture of isotopesAtoms which have the same number of protons (so they are atoms of the same element) but they have a different number of neutrons (so they have a different mass number)., each present in a different amount.
The term ‘weighted mean mass’ takes into account the different contribution of each isotope to the overall mass.
The contributions of all isotopes are combined to give the relative atomic massThe mass of the atom compared with that of the carbon-12 isotope, which has a mass of exactly 12. – the weighted mean of the mass numbers.
mass numberThe number of protons and neutrons found in the nucleus of an atom. are whole numbers because they are the number of protons plus the number of neutrons.
Relative atomic mass is an average mass, which takes into account all of the isotopes and their abundance. It is not always a whole number. However, on your data leaflet, apart from chlorine, the relative atomic masses have been rounded to whole numbers.
