1. History Wrap-Up & Radiation Intro

2. Warm-Up
Complete the History and Scientist ½ Sheet

3. Atomic Structure Review

4. History of the Atom Notes

5. Democritus (400 BC) Greek Philosopher
All matter is composed of tiny, indivisible parts called “atomos”
He said you cannot cut a piece of matter infinitely, but at some point you would get the smallest piece of matter possible.
Said “atomos” could not be divided any further

6. John Dalton (1803) School Teacher
Studied the ratios in which elements combine in a chemical reaction
Dalton’s Atomic Theory
All matter is composed of tiny indivisible parts called atoms (they can be broken down further, although properties will not be retained)
Atoms of the same element are exactly alike, atoms of different elements are different (not all atoms of the same element have the same mass – isotopes)
Atoms can combine in simple ratios to form compounds
Atoms are neither created nor destroyed
- Atoms cannot be destroyed, they simply rearrange in a chemical change, therefore the total amount of atoms remains the same

7. John Dalton (1800’s)

8. J.J. Thomson (1897) He created the “plum pudding model” of the atom.
Discovered the electron
Worked with Cathode Ray Tubes
Discovered particles with a negative charge, electrons – knew they were negative charges by the deflection of the beam from a magnet
He also was able to estimate that the mass of the electron was equal to about 1/1800 of the mass of a hydrogen atom.
His discovery of the electron won the Nobel Prize in
He created the “plum pudding model” of the atom.
“Pudding” is positive
Electrons are embedded within the “pudding”

9. J.J. Thomson (1897)

10. J.J. Thomson (1897)
Discovered that the beam going between the anode and cathode could be deflected by bringing a magnet close to the cathode ray tube. The deflection that Thomson observed showed that the beam must have been made up of negatively charged particles
He showed that the production of the cathode ray was not dependent on the type of gas in the tube, or the type of metal used for the electrodes. He concluded that these particles were part of every atom.

11. Robert Millikan (1909)
measured the charge of an electron using the oil drop experiment.
x-rays gave the oil a negative electron
1.60x10^-19 coulomb is the charge of an electron
using Thomson’s charge to mass ratio, he determined the mass of the electron is 9.11x10^-28g

12. Oil Drop Experiment

13. Ernest Rutherford (1911) Born in New Zealand 1871-1937
Tested Thomson’s theory of atomic structure with the “gold foil” experiment in 1910.
Bombarded thin gold foil with a beam of ‘alpha’ particles.
If the positive charge was evenly spread out, the beam should have easily passed through.
All of the positive charge and most of the mass of an atom are concentrated in a small core, called the nucleus.
Gold Foil Experiment (alpha scattering)
he determined that an atom’s positive charge and most of its mass was concentrated in the core (most of the atom is empty space)
he named the core “the nucleus”

14. Rutherford’s Gold Foil Experiment

15. Rutherford’s Model of the Atom
Contained a positive nucleus
Electrons were around the outside of the nucleus

16. Niels Bohr (1914) Start of the Quantum Mechanical Model
Electrons are particles
Electrons occupy different fields or energy levels
Based on the fact that atoms appeared to release fixed amounts (quantized) of energy when exposed to heat
When an electron is exposed to an energy source, it jumps to a higher energy level
When the electron eventually falls back to its original position, energy is released

17. Niels Bohr (1914)

18. Werner Heisenberg Principle of uncertainty
We cannot know both the location and the momentum of an electron
The more we know about an electron’s position, the less uncertain we are

19. Erwin Schrödinger (1926)
Based on Heisenberg's principle of uncertainty
Shows where electrons will probably be found by using the waves they leave behind
Electrons are waves
Update to the Quantum Mechanical Model
Sometimes called the Electron Cloud Model

20. Erwin Schrödinger (1926)

21. Maryland Nuclear Power Plant
Images taken from NRC
Calvert Cliffs is Maryland’s nuclear power plant

22. What region of the United States has the highest concentration of nuclear power plants? Why?

23. Nuclear Power Plants
map: Nuclear Energy Institute

24. Because of the large quantity of energy produced using nuclear power plants. It is important to understand the process of how the energy is created.

25. There are 3 main types of radiation that produce energy
Alpha
Beta
Gamma
Today you will research the three types of radiation

26. Task: Complete the Radioactive Particles Chart
Use Chapter 4 p. 122 – 125 in the textbook to complete the chart
Use your electronic device to research how the radiation can be blocked and practical uses.