1. Atomic Theory Grade 9 Science

2. Theories and Laws What’s the difference between a theory and a law??

3. Laws  Descriptions of events or patterns that have been observed over long periods of time  Do not involve an explanation, simply state what happens

4. Theories  Explain observations that are supported by experimental evidence  Can change if new evidence becomes available

5. Development of the Atomic Theory Men and women from different countries have contributed to our understanding of the atom

6. Early Greeks contributed to the Atomic Theory Empedocles: http://en.wikipedia.org/wiki/Empedocles http://en.wikipedia.org/wiki/Empedocles Democritus: http://www.timelineindex.com/content/view/1228 Aristotle: http://cstl-csm.semo.edu/mcgowan/ch181/atomhist.htm

7. John Dalton 1766 - 1844

8. Dalton Atomic Theory State the 4 points of Daltons Atomic Theory: 1 2 3 4

9. JJ Thomson 1856 - 1940

10.  Atoms composed of small particles  Atoms contain negatively charged particles called electrons  Raisin bun model

11. Ernest Rutherford 1871 - 1937  Conducted “Gold Foil Experiment”  Realized large space within atoms  Discovered the nucleus of the atom  Established that the nucleus had 2 types of particles: proton (+) and neutron (0)

12. Gold Foil Experiment Positive particles

13. Neils Bohr 1885 - 1962  Studied the area around the nucleus  Area around nucleus contained electrons (-)  Ran electric current through gas and observed the gas glowing brightly  Proposed electrons surround nucleus in specific energy levels

14. Bohr’s ModelGlowing Neon Gas

15. Study the structure of the Atom with its three sub- atomic particles