Fri February 25, 2011 By: Sonu Verma

is there any difference between mass number andatomic weight?

Expert Reply
Sat February 26, 2011
Dear student,
Mass number is the mass of a particular isotope of an element relative to hydrogen-1. Atomic weight or more correctly atomic mass is a weighted mean of the masses of the naturally occurring isotopes. So for chlorine for example there are isotopes withmass numbers 35 & 37 and at their natural abundance the atomic mass of Cl comes out at about 35.5
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