The isotope 121sb makes up 57.21% of naturally occurring antimony. The only other naturally occurring isotope is 123sb. Deduce the relative atomic mass of antimony according to this data. How do I do that?
The ponderate media between both isotopes gives 121.86.
In each 100
Assuming the mass of the isotopes is integer (they are close to it) we may calculate the corresponding mass of that amount:
As this correspond to 100 mol the atomica mass is:
The real value is
As you are talking about relative atomic mass, take the units out, so the answer is only 121.86