Question

The element antimony has an atomic weight of 121.957 amu and only two naturally-occurring isotopes. One isotope has an abundance of 61.30% and an isotopic mass of 120.804 amu. Based on this data, what is the mass of the other isotope?

Answer 1

46.726 amu

Step-by-step explanation:

The total abundance of the two isotopes of antimony is 100%, so the abundance of the other isotope is 100% - 61.30% = 38.70%.

Since the atomic weight of antimony is 121.957 amu, the total mass of the two isotopes is 121.957 amu. The mass of the second isotope can be calculated as follows:

mass of the second isotope = (total mass of the two isotopes) * (abundance of the second isotope) / 100

mass of the second isotope = 121.957 amu * 38.70% / 100

mass of the second isotope = 46.726 amu

So the mass of the other isotope is 46.726 amu.