1. Check Understanding Question
Task: Individually, read the following question and write down your answer in your
notes, to check your understanding of physical and chemical change.

2. How can we know what atoms look like if we can’t see them?
Focusing Question
How can we know what atoms
look like if we can’t see them?

3. Models or

4. How can we know what atoms look like if we can’t see them?
Lead
Gold
*Alchemists tried to use experiments to turn lead into gold*

5. Introducing Atomic Theory
How can we know what atoms
look like if we can’t see them?
Introducing Atomic Theory
Greek philosopher Democritus in 400 B.C. used the word atomos to describe the smallest particles that could not be broken further. Atomos means “indivisible.”  Democritus stated that each type of material was made up of a different type of atomos. These different particles, he believed, gave each material its own unique set of properties.

6. How can we know what atoms look like if we can’t see them?
Dalton’s Model
-Each element is made up of atoms of the same mass (weight)
-Different elements have different masses
Each atom is a tiny sphere
Billiard (pool)
Ball Model

7. Hydrogen

8. How can we know what atoms look like if we can’t see them?
Thompson’s Model
-Conducted the Cathode Ray Experiment
-Discovered that inside the atom are negatively charged electrons
Raisin Bun

9. How can we know what atoms look like if we can’t see them?
Rutherford’s Model
Solar System Model
-Conducted a Gold Foil
Experiment
-Discovered that the positive
particles are in the center of
the atom, which are called
protons

10. How can we know what atoms look like if we can’t see them?
Bohr’s Model
Atomic Model
-Suggested that
electrons do not
randomly travel in an
atom
-Electrons travel in
electron shells

11. Rules for Creating Bohr Models of Elements
How can we know what atoms
look like if we can’t see them?
Rules for Creating Bohr Models of Elements
The row number of the periodic table that the element is in, tells you how many shells you need
The 1st electron shell can only hold 2 electrons
The 2nd and 3rd electron shells can only hold 8 electrons
You indicate (write) the number of protons and neutrons in the nucleus