1. Chapter 2 Matter is made up of Atoms
Average Atomic Mass

2. Atomic Mass
Atomic Mass: mass of an atom expressed in atomic mass units.
Atomic Mass Unit: u = amu
Average Atomic Mass
Mass found on the Periodic Table  average of the masses of the naturally occurring isotopes of each element.
Weighted Average.

3. Atomic Mass
Sample Problem
 What is the atomic mass of copper if 69.17% of its atoms have a mass of amu and 30.83% of its atoms have a mass of amu?

4. Atomic Mass
Step 1: Change any percentage to decimal. (move decimal point two spots to the left.)
Step 2: Multiply decimal by atomic mass.
Step 3: Add Step 2 numbers together.

5. Atomic Mass Copper (Cu) 69.17% is 62.94 amu. 30.83% is 64.93 amu.
Step 1
Step 2
Step 3
69.17% =
30.83% =
x 62.94
x 64.93 =
63.56 amu

6. Atomic Mass

7. Chapter 2 Matter is made up of Atoms
Ions.

8. Recap No 1 – The Atom Proton Neutron Electron Charge +1 -1 Mass 1 amu-1
Mass
1 amu
0 amu
Location
Nucleus
Orbit

9. Recap No 2 – Periodic Table
Key
Description
Element Name
Type of Atom
Element Symbol
Shorthand
Atomic Number
# p+ = # e-
Atomic Mass
# p+ and # n0

10. Recap No 3 – Isotopes Same number of protons and electrons.
Different number of NEUTRONS.
Isotope
Protons
Neutrons
Mass
Protium 1
Deutrium 2
Tritium 3

11. Recap No 4 - Atomic Mass Copper (Cu) 69.17% is 62.94 amu.
Step 1
Step 2
Step 3
% to Decimal
69.17% =
30.83% =
Multiply by AMU
x 62.94
x 64.93
Add together =
63.56 amu

12. Simple Ions. Ion: charged atoms. How does this happen?
Add or remove electrons…

13. Simple Ions. Cation: Lose electrons; becomes positive. “Plussy Cat”
Usually metals.
“Plussy Cat”

14. Simple Ions. Anion: Gain electrons; becomes negative. “Ant-ion”
Usually Nonmetals
“Ant-ion”

15. Calculating #e-
p+ = 8
e- = ? -2
p+ = 14 +4 10 10

16. Simple Ions Electrically charged atoms.
Result from the gain or loss of an electron.
Element + electron = negative charged element (anion)
Element – electron = positive charged element (cation)

17. Ions Examples: 3 4 2 20 18 13 14 10 9 16 Lithium – Li +1
Ion Name
Protons
Neutrons
Electrons
Lithium – Li +1 3 4 2
Calcium – Ca +2 20 18
Aluminum – Al +3 13 14 10
Fluorine – F-1 9
Sulfur – S-2 16