1. Counting Atoms

2. Atoms What is the Atomic Number of an element?
What is the Atomic Mass of an element?
What is the difference between average atomic mass and mass number?
Why is the average atomic mass (the one with the decimals) more useful sometimes?

3. Counting Large Numbers
The astronomical unit (AU or au or a.u. or sometimes ua) is a unit of length approximately equal to the distance from the Earth to the Sun. The currently accepted value of the AU is 149,597,870,691 ± 30 metres (nearly 150 million kilometres or 93 million miles).
Very Large Distance!!!

4. Scientific Notation Review
= 6.0 x 10 9
= 4.67 x 10 8
= 5.23 x 10 5
Very small numbers
= 7.2 x 10 -7
= 4.5 x 10 -4
0.001 = 1.0 x 10 -3

5. Counting atoms Atoms are VERY small
How do you quantify such a small substance
Mole: exactly 12 grams of carbon-12
Molar mass: mass in grams of one mole of an element
Carbon -12 = 12 grams

6. Counting atoms 1 mole of any substance posses 6.022 x 1023 particles
This number Is Avagadro’s Number

7. Practice What is the molar mass of 5 elements?
How many particles are in the above amounts?
How many particles are in 1 mol of
Eggs
Pizza slices
Grapes
Practice problem B pg 85, 1-4 Problems C, 1-3 and a signed “Assignment Report”!!!