Antimony consists of two major isotopes with the following atomic masses: 121sb (120.904 amu) and 123sb (122.904 amu). the average atomic mass of antimony is 121.760 amu. calculate the percent of each of the isotopes. report your answer to 3 significant figures.

121Sb=57.2%

123Sb=42.8%

Explanation:

We are given that

Atomic mass of 121Sb=120.904 amu

Atomic mass of 123Sb=122.904 amu

Average atomic mass of antimony=121.760 amu

We have to find the percent of each of the isotope.

Let x be the percent of 121Sb and 1-x be the percent of 123Sb.

Using formula of average atomic weight

Average atomic weight=atomic weight of 121Sb percentage abundance of isotope 121Sb+atomic weight of 123Sbpercentage abundance of isotope 123Sb

Substitute the values

Percentage of 121Sb=57.2%

Abundance of isotope 123Sb=1-0.572=0.428

Percentage of isotope 123Sb=42.8%