Problem: Magnesium has three naturally occurring isotopes: 24 Mg (23.985 amu) with 78.99% abundance, 25 Mg (24.986 amu) with 10.00% abundance, and a third with 11.01% abundance.Look up the atomic weight of magnesium, and then calculate the mass of the third isotope.

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FREE Expert Solution

We’re being asked to calculate the mass of the third isotope of magnesium. We can use the following equation:


Atomic Mass = [mass×f.a.]isotope 1+[mass×f.a.]isotope 2......



where atomic mass = average atomic mass of the element and f.a. = fractional abundance of the isotope. To get f.a., we simply need to divide the given percent abundance by 100.


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Problem Details

Magnesium has three naturally occurring isotopes: 24 Mg (23.985 amu) with 78.99% abundance, 25 Mg (24.986 amu) with 10.00% abundance, and a third with 11.01% abundance.

Look up the atomic weight of magnesium, and then calculate the mass of the third isotope.