Question

The element antimony exists in nature as two isotopes: has a mass of 120.9038 u and has a mass of 122.9042 u.The average atomic mass of antimony is 121.76 u. Calculate the relative abundance of the two antimony isotopes.

Answer 1

The percentage relative abundances of isotopes are 56.20% and 43.80%

Step-by-step explanation:

• Relative atomic mass of an element is calculated by getting the average mass of all the atoms of an element relative to 1/12th the mass of carbon-12 atom.
• It is calculated by getting the average of the product of relative abundance by the mass of each atom.

In this case;

Average atomic mass = 121.76 u

Mass of the first isotope = 120.9038

Mass of the second isotope = 122.9042

Assuming the relative abundances are;

1st isotope = x %

2nd isotope = (100-x)%

Therefore;

121.76 = ((120.9038x) + (100-x)(122.9042)) ÷ 100

12176 = 120.9038x + 12290.42 -122.9042x

-114.42 = -2.0004x

x = 56.20%

100-x = 43.80%

Therefore, the percentage relative abundances of isotopes are 56.20% and 43.80%