average atomic mass

Question

Calculate the atomic mass for magnesium given the following data for its natural isotopes.

: 23.985 amu, 78.70%

: 24.986 amu, 10.13%

: 25.983 amu, 11.17%

Answer 1

Hello, Chris,

Take the percentage of each isotope and multiply it times that isotope's mass (in amu). That wwill be the contribution of that isotope to the final attomic mass. Add the three numbers to find the weight-averaged atomic mass for Mg. I find 24.310, to 5 sig figs.

Bob