1. Isotopes

2. Isotopes Are…. Atoms w/ same # of p+ but different # no
different mass # s
chemically alike- react the same way
b/c identical # of p+ & e-
Atomic Mass rounds to most abundant isotope

3. Atomic Mass Formula
( Mass* % Abundance) + (Mass * %Abundance)+…

4. Example 1
Mass (amu) x Abundance (%) = Relative Mass 35Cl x = amu Cl x = amu 100 Atomic mass of Cl = amu

5. Example 2
Two isotopes of gallium are naturally occurring with 69Ga at 60.11% (68.93 amu) and 71Ga at 39.89% ( amu). What is the atomic mass of gallium?