2.2 - Relative Mass

Carbon-12

the mass of an atom:

1) a standard isotope is needed to base all atomic masses (carbon- 1.992646538*10^-26 kg)

2) working in Kg would be very awkard so a mew unit called atomic mass unit "u" is used.

3) for carbon this is 12 u/ the standard mass for 1 atomic mass is 1 u (1/12th of a carbon-12)

4) 1 u is approximately the mass of a proton or neutron

Relative Isotopic Mass

= the mass of an isotope relative to 1/12 th of the mass of a carbon-12 atom.

this has no units as it's a ratio…