J.R. S. answered • 09/06/18
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With more than one isotope, the atomic mass is the weighted average of the isotopes. Thus, ...
One isotope has an abundance of 57.4%, so the other has an abundance of 42.6%.
(120.9038)(0.574) + (122.9042)(0.426) = 69.3988 + 52.3572 = 121.7559 = 121.76
The element is Sb, antimony.
J.R. S.
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Since one isotope is 57.4% the other has to be 42.6% in order for the total to add up to 100%. So 100 - 57.4 = 42.6%
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09/18/19
Julia P.
How did you find 42.6%?09/18/19