1. Drill Take out HW and Periodic Table
Are the following elements metals, nonmetals, or metalloids??
Calcium (Ca)
Arsenic (As)
Uranium (U)
Chlorine (Cl)
Aluminum (Al)

2. Agenda Drill History of the Atomic Model Exit Slip Video Demos
Investigation
Exit Slip

3. I Can… Create a timeline of the history of the atom
Explain the discoveries (in detail) of Thomson’s and Rutherford’s experiments

4. What is an Atom? The basic unit of matter Latin word – atomos
Means “that which can’t be split”
Not totally true since there are subatomic particles

5. How big is an Atom?

6. Working with pico (10-12)
Scanning tunneling microscope

7. 5 Scientists John Dalton J.J. Thomson Ernest Rutherford James Chadwick
Niels Bohr

8. John Dalton England, 1808 Atomic Theory which states:
All matter is made up of atoms
All atoms of a given element are identical in mass and properties
Compounds are formed with a combination of 2+ different kinds of atoms
A chemical reaction is the arrangement of atoms
Atoms are indivisible and indestructible
**NOTE: Not true today!!

9. Dalton Model Diagram:
Shading is used in the sphere to show that it’s solid throughout.

10. J.J. Thomson Demo In your group…
Look at the data and what you saw in the demo
Determine:
What J.J. Thomson found in the modern-day atom
How J.J. Thomson represented the atom (how its drawn)

11. Discovery of electrons
Cathode Ray Tube Experiment
J.J. Thompson reasoned that if Dalton’s ideas about the indestructibility of an atom were true, how could negatively charged parts of atoms (the electrons) be released from the atom?

12. J.J. Thomson England, 1897 Discovery Atoms contain electrons
"There is no other branch of physics which affords us so promising an opportunity of penetrating the secret of electricity.” - J.J. Thomson
England, 1897
Discovery
Atoms contain electrons

13. Thomson Model Diagram
This model is referred to as the ‘Plum Pudding model.’ Thomson believed that the atom consisted of a positive sphere (the pudding) with electrons embedded in it (the raisins). + -

14. Plum Pudding

15. Blueberry Muffin
Electrons = Blueberries
Positive Charge = “cake” part

16. Rutherford In your group…
Look at the data and what you saw in the demo
Determine:
What Rutherford found in the modern-day atom
How Rutherford represented the atom (how its drawn)

17. Rutherford’s Gold Foil Experiment
Positively charged radiation directed towards a thin sheet of gold foil.
Odd results: most radiation went through the foil, some scattered at wide angles, and some shot back at him!

18. Ernest Rutherford New Zealand, 1911 Discovery
Atoms are made up of mostly empty space
Atoms contain a small, dense, positively-charged nucleus.

19. Rutherford’s Model Diagram+ -

20. Rutherford Video

21. Niels Bohr Denmark, 1913 Discovery:
Electrons contain specific amounts of energy and orbit the nucleus in specific paths, called energy levels
Electrons must gain energy to move to a higher energy level or lose energy to move to a lower energy level

22. Bohr Model Diagram
The small particles in the center represent the protons and neutrons in the nucleus. e-

23. James Chadwick England, 1932 Discovered the neutron
When looking at the masses of elements, found that they increased, but the electron does not have much weight
Concluded that there must be something else in the nucleus that did not have a charge

24. Exit Slip
Please complete the exit slip! 

25. Quantum Theory . 1925 – present
Erwin Schrödinger, Wolfgang Pauli, Max Born. Max Planck and Werner Heisenberg Discovery:
Electrons behave more like waves than particles.
The location of an electron is given in terms of probability. The exact location of an electron is impossible to determine
Energy levels exist, but the electrons exist in electron clouds, not in specific paths
PROBABILITY CLOUDS! .

26. Bohr Video