A hypothetical pure element consists entirely of two isotopes. The natural percent abun- dance of the isotope with mass 25.6 u is 47.2%. The other isotope has mass 29.7 u. Calculate the atomic weight of the naturally occurring element.

Answer 1

The atomic mass of an element that you see in the periodic table is the weighted average of all of the isotopes. 100-47.2 = the other isotope %.
(25.6 u x 0.472) + (0.297 u x (1.00 - 0.472) = ?