2 Average of IsotopesEvery element typically exists in several isotope formsIsotopes are atoms of the same element with different numbers of neutronsEven though there are several isotopes of the same element, we only see one square given to each element on the periodic table
3 The mass recorded on the periodic table is a weighted average of all the naturally occurring isotopes of the element
4 ExampleChlorine is found in two isotope forms. One has a mass of amu, the other a mass of amu. The first makes up 75.5% of the sample. What is the average atomic mass of the chlorine?
5 The average atomic mass is 35.5 amu To solve, multiply the mass of each isotope with its percent abundance, then add(34.97)(.755) + (36.97)(.245) = amuThe average atomic mass is 35.5 amu
6 Example 2 Zinc has 5 stable isotopes as shown 48.89% 63.9291 amu Find the average atomic mass of Zn.