How can chlorine have an atomic mass of 35.45⋅amu?

1 Answer
anor277
Mar 7, 2017

The atomic mass quoted on the Periodic Table is simply the WEIGHTED average of the individual isotopic masses of an element.

Explanation:

We can calculate the average atomic mass of the element chlorine, given that its isotopic distribution is: 35Cl,75.53%;37Cl,24.47%.

And the weighted average of the masses is:

(0.7553×35+0.2447×37)⋅amu

= 35.46⋅amu, which is very near the atomic mass quoted on the Periodic Table (they are slightly different because the Table considers minor isotopes).

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