1. Unit 2: Atomic Theory & Structure
The Mole & Mole-Particle Conversions

2. Counting Objects One way to measure objects is to count them.
Apples are easy to count
Grains of sand are difficult to count (too small)

3. Counting Objects Grouping objects can make counting easier.
Eggs are counted by the dozen (12)
Copy paper is counted by the ream (500 sheets)

4. Counting Objects Grouping objects can make counting easier.
Particles (atoms, molecules, etc.) are counted by the mole (6.02 x 1023)

5. What is a mole?
It’s not a spy, a machine for digging tunnels, a burrowing animal, or a spot of skin pigmentation, it’s…
Avogadro’s Number

6. How big is a mole?
A mole of soda cans would cover the surface of the earth to a depth of over 200 miles!

7. How big is a mole?
A mole of popcorn kernels spread across the Unites States would have a depth of more than 9 miles!

8. Why is the mole useful?
The mole helps measure atoms in a more manageable way because atoms are so small!
One mole of iron contains 6.02 x 1023 atoms, but they fit into a small beaker!

9. Learning Check
Suppose we invented a new collection unit called a rapp. One rapp contains 8 objects.
1. How many paper clips in 1 rapp?
a) 1 b) 4 c) 8
2. How many oranges in 2.0 rapp?
a) 4 b) 8 c) 16
3. How many rapps contain 40 gummy bears?
a) 5 b) 10 c) 20

10. Avogadro’s Number as Conversion Factor
6.02 x 1023 particles
1 mole or
1 mole
Note that a particle could be an atom OR a molecule!

11. Conversions using Avogadro’s number as a conversion factor
Type 1
Moles Particles
given mol x 6.02 x 1023 atoms = ______ atoms
1 mol
Type 2
Particles Moles
Mole = Latin “pile, heap, or mass”
Given atoms x mol = ___ mol
6.02 x 1023 atoms

12. Type 1 Moles Particles 2.12 mol x ______________ = 1 mol
How many molecules are in 2.12 mol of propane gas (C3H8) ?
2.12 mol x
______________ =
1 mol
6.02 x 1023 molec = ______ molec
1.28 x 1024 molec
in a BOX!!!

13. Type 2
Particles Moles
1 mol ___ mol
1.25 x 1023 atoms x
_____________ =
6.02 x 1023 atoms
0.208 mol
in a BOX!!!

14. How many moles is 2.17 x 1024 molecules of Br2 ? Type 2
Particles Moles
2.17 x 1024 molecules x
________________ =
6.02 x 1023 molecules
1 mol ___ mol
3.60 mol
in a BOX!!!