Gallium consists of 2 isotopes. One of those isotopes is Ga-71 with a mass of 70.92 amu with an abundance of 39.892%. What is the mass number of the other isotope?
We’re being asked to calculate the mass number of the other isotope of Gallium-70 (Ga-70).
We can use the following equation:
atomic mass = average atomic mass of the element
f.a. = fractional abundance of the isotope.
To get f.a., we simply need to divide the given percent abundance by 100.