Question

# Calculate the average atomic mass of chlorine.

Solution

## Chlorine exists in two isotopes. Multiply the mass of each chlorine isotope by its percentage of abundance (in decimal form) and add together:  (34.968852714×0.75784)+(36.965902605×0.24224)  = 26.5... + 8.9546...  = 35.455 (approx.)  This is the same as in the periodic table because the atomic weights in the periodic table are an average weight taking into account the relative amount of each isotope present in a random sample of the element.

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