What does relative atomic mass mean?
Relative atomic mass is a synonym for atomic mass. The relative atomic mass of an element is the average of the isotopic masses, weighted according to the naturally occurring abundances of the isotopes of the element. In a weighted average, we assign greater importance – give greater weight – to the quantity that occurs more frequently. Since carbon-12 atoms are much more abundant than carbon-13 atoms, the weighted average must lie much closer to 12 than to 13. The result that we get by applying the following general equation where the right hand side of the equation includes one term for each naturally occurring isotope: (Relative) Atomic Mass = (fractional abundance of isotope 1 x mass of isotope 1) + (fractional abundance of isotope 2 x mass of isotope 2) + … The mass spectrum of carbon shows that 98.892% of carbon atoms are carbon-12 with a mass of exactly 12u and 1.108% are carbon-13 with a mass of 13.00335u. [98,992 atoms of carbon-12 (12 u exactly)]+ [1,108 atoms of carbon-13
