🤓 Based on our data, we think this question is relevant for Professor Snaddon's class at IU.
We’re being asked to calculate the mass of the third isotope of magnesium. We can use the following equation:
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.
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.