1.12 calculate the relative atomic mass of an element from the relative abundances of its isotopes

RELATIVE ATOMIC MASS (Ar):

- Calculated by (% of the isotope x the relative abundance) + (% of the isotope x the relative abundance) / 100

- Chlorine:
Atomic mass = 35 + 37
Abundance = 3 + 1
- Therefore 2 isotopes of chlorine (Cl); (³⁵Cl) and (³⁷Cl).
- The abundance shows that for every 3 atoms of (³⁵Cl), there is 1 atom of (³⁷Cl).
- So now you multiply the relative atomic mass by its abundances.
- Add them together.
- Divide them by the total amount of abundances.

- (35 x 3) + (37 x 1) / (3 + 1)
- = 35.5