1. Calculating Average Atomic Mass

2. Learning Target
I will be able to calculate average atomic mass and understand what a mole is.

3. Average Atomic Mass
It’s the decimal number found on the periodic table.
Average of the masses of all the isotopes of an element considering the percentages in which they naturally occur.
For all of the atoms of an element.

4. Steps for Calculating Average Atomic Mass
1. List the isotopes and their masses
2. Multiply the mass of each isotope by its percent occurrence (in decimal form)
78% = 0.78
3. Add the results.
4. Check and make sure that your answer falls between the lowest and highest masses in your original problem.

5. Sample Problem
In nature a sample of Neon contains 90.0% Ne-20 with a mass of amu and 10.0% Ne-22 with a mass of amu. What is the average atomic mass?
Ne-20… amu
Ne-22… amu

6. UNITS for Avg. Atomic Mass
Amu – atomic mass unit (1/12 of a carbon-12 atom) = mass of 1 proton or neutron
Grams/mole (g/mol)
What is a mole?......

7. 6.02 x 1023 particles, pieces or molecules…
A mole is…
A small rodent that burrows underground
OR….
6.02 x 1023 particles, pieces or molecules…

8. Avogadro's Number…
Another name for a mole!!!

9. Let’s think about it….

10. 1 mole of Copper
Has a mass of…
63.55 grams

12. We love moles!!!!!