2.  Each element on the periodic table has an isotope.  What make an element have different isotopes?  There are 2 different isotopes of iron  Find the PEN of iron– 55 & iron– 56

3. 11  Atomic mass: the weighted average mass of ALL the isotopes of that element.  This number is located on the bottom of each block on the periodic table  Not a whole number  Different from the Mass #

4.  A piece of carbon will contain both carbon-12 & carbon-14.  Carbon-12 is found in 98% of the sample.  Carbon-14 is found in 2% of the sample.  What is the average atomic mass of carbon?

5.  Change percent to decimal  Multiply the decimal by the mass # of that isotope  Then add the two sums together.  Answer must have units  98% =.98  2% =.02 .98 x 12 = 11.76 .02 x 14 = 0.28  11.76 + 0.28 = 12.04  12.04 amu

6. 1. 80% 127 I, 17% 126 I, 3% 128 I 2. 50% 197 Au, 50% 198 Au 3. 99% 1 H, 0.8% 2 H, 0.2% 3 H 4. 95% 14 N, 3% 15 N, 2% 16 N 5. Pg. 121 18 – 22