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?

Question

Serenity Allen · Accepted Answer

The ponderate media between both isotopes gives 121.86.

In each 100 #mol# of Sb you have: #57.21# mol of # _ ^(121)Sb# and #100-57.21=42.79 mol# of # _ ^(123)Sb# Assuming the mass of the isotopes is integer (they are close to it) we may calculate the corresponding mass of that amount: #57.21xx121+42.79xx123=12185.58 g# As this correspond to 100 mol the atomica mass is: #12185.58/100=121.86 g//(mol)#. The real value is #121.76 g//(mol)# for comparison. As you are talking about relative atomic mass, take the units out, so the answer is only 121.86

Caleb Adams · Answer

undefined To deduce the relative atomic mass of antimony based on the given data, you can use the following formula:

$$ \text{Average atomic mass} = (\text{isotope 1 mass} \times \text{isotope 1 abundance}) + (\text{isotope 2 mass} \times \text{isotope 2 abundance}) $$

Given:
- Isotope $^{121}_{51}\text{Sb}$ makes up 57.21% of naturally occurring antimony, with a mass of approximately 120.9038 u.
- Isotope $^{123}_{51}\text{Sb}$ is the only other naturally occurring isotope, with a mass of approximately 122.9042 u.

Substitute these values into the formula to find the average atomic mass of antimony.