1. Activity #13 Atomic Theory: How do we know what atoms are made of?
In science, we use models to help us understand particles, like atoms, that are too small to see.
The following slides show how scientists were able to discover the parts and function of the atom.

2. Station 1:Democritus (400 BC)
Ancient Greek philosopher
Believed that everything in the universe was made of indivisible particles called “atoms” (or “atomos” in Greek)
Said atoms were constantly moving
Atoms only differed in shape, position, and arrangement

3. Democritus Cont’d

4. Station 2: John Dalton (1803)
Visualized atoms to look like a pool ball/bowling ball
All elements are made of atoms.
All atoms of the same element are exactly alike and have same mass.
An atom of one element cannot be changed into an atom of a different element.
Atoms cannot be created nor destroyed, only rearranged.
Compounds are made from atoms of different elements.

5. John Dalton Cont’d

6. Station 3: J.J. Thomson (1897)
Visualized the atom to look like a chocolate chip muffin or plum pudding
An atom consists of negative charges scattered throughout a ball of positive charges.
Proved that an atom could be divided
Said the atom is neutral.

7. JJ Thomson Cont’d

8. Station 4: Ernest Rutherford (1908)
Rutherford was a student of Thomson.
Visualized the atom to look like a peach
Positive charge (protons) is located in the center of the atom.
Center is called the nucleus.
Almost all of the atom’s mass is located in the nucleus.
Atom is mostly empty space with the electrons moving around the nucleus.

9. Ernest Rutherford Cont’d

10. Station 5: Niels Bohr (1913) Student of Thomson and Rutherford
Visualized the atom to look like a sliced red onion & planets in the solar system
Electrons orbit around the nucleus in a definite orbit
Electrons could have only specific amounts of energy, leading them to move in certain orbits

11. Niels Bohr Cont’d

12. Station 6: The Electron Cloud Model (1920s)
Electrons do not move in a definite path
It is impossible to determine the exact location of an electron
The atom has a small, positively charged nucleus, surrounded by the electron cloud

13. The Electron Cloud Model Cont’d

14. Station 7: Atoms of Different Elements
Using the cards at your table, count up the number of protons, neutrons, and electrons in the atoms of the following elements:
Copper
Carbon
Aluminum
Sulfur

15. Station 8: Learning Goal
I can:
Describe the basic structure of the atom.
Explain how the idea of the atom has changed over time.

16. Station 9: Organize your Notebook!
Quarter 1 1. Class Norms 8/7/17 2. Spongebob Lab Safety 8/9/17 3. What's Wrong? 8/10/17 4. Science Lab Equipment 8/11/17 5. Chemicals in Your Eye 8/14/17 6. Observation and Inference 8/15/17 7. Variables 8/17/17 8. Writing a Hypothesis 8/18/17 9. Variables Lab 8/21/ Reading and Interpreting Graphs 8/22/ What is Matter? 8/29/ Atomic Structure 8/31/ Atomic Theory 9/1/17