What Is the Atomic Mass of Element A with Given Isotopes and Abundances?

[CMATT]

Homework Statement

Suppose the element A contains three isotopes, 86A (atomic mass 85.909 u, abundance 16.19%) 87A (atomic mass 86.908, abundance 7.00%) and 88A (atomic mass 87.906 u). What would be the atomic mass of A that would appear in the periodic table?

Homework Equations

(A1 x %A1) + (A2 x %A2) + (A3 x (1-(%1 +%2)) = answer

The Attempt at a Solution

16.19% + 7.00% = 23.19%

100% - 23.19% = 76.81% --> so that would be the 88A abundance % right?

then I'm confused from there. Please help

 

[mfb]

100% - 23.19% = 76.81% --> so that would be the 88A abundance % right?

Sure.

then I'm confused from there. Please help

Just plug everything into the equation you have.