Verify that the atomic mass of magnesium is 24.31, given the following information:
24Mg, mass = 23.985042 u
percent abundance = 78.99%
25Mg, mass = 24.985837 u
percent abundance = 10.00%
26Mg, mass = 25.982593
percent abundance = 11.01%
The average atomic mass is given as a weighted average of the atomic masses of each isotope.
atomic mass = Σ all isotopes (atomic mass) x (fractional abundance)
What is the fractional abundance of 24Mg?
Thank you for your answer, but what is the fractional abundance then?
1 Answer
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Simplifying the given equation a bit so it’s more understandable,
atomic mass = (isotope 1 abundance 1) + (isotope 2 abundance 2) + (isotope 3 * abundance 3)
You would continue that pattern if there were more isotopes.
So then: atomic mass = (23.985042 * 0.7899) + (24.985837 * 0.1000) + (25.982593 * 0.1101) = 18.945784 + 2.498584 + 2.860683 = 24.305051 = 24.31
