2.  Identify who came up with the first theory of atoms?  Discuss what Dalton added to the atomic theory?  Explain how JJ Thomson discovered the electron?  Describe Rutherford’s atomic model?

3. 1. Electron 2. Proton 3. Neutron 4. Nucleus

4.  Over 2000 years ago Greek philosopher, Democritus of Abdera  First stated that all matter was made of representative particles  He called these particles atomos- literally translated indivisible or unbreakable  Why was this such an educational risk?  He had no evidence to support his claim

5.  Since Democritus lacked evidence, many other theories were proposed  Chemistry did not become a science of measurement until the 1700’s  Between the time of Democritus and the 18 th century alchemy reined  One main goal of alchemists was to turn inexpensive materials into gold!  Did they succeed?

6.  One century later, John Dalton, a school teacher, published his theory on atoms  He first suggested that atoms can join other atoms to form compounds  He also stated that all atoms of the same element are exactly alike (we will find out later that this is not exactly true)

7.  Dalton, unlike Democritus, used evidence to support his theory of atoms  Dalton conducted experiments and noticed that certain substances actually behave in predictable ways (Water reaction video) 2H 2 + O 2  2H 2 O  He also noticed that they happen in specific proportions.

8.  At the end of the 1800’s JJ Thompson conducted an experiment using a Crooke’s tube.  This is basically like the tube in old (not plasma, LCD, or projection) TV’s  The rays observed in these tubes were constructed of negatively charged parts of the atom.  This proved that atoms could be divided into smaller parts So…the word atom is a misnomer… a mis-no-WHAT!?

9.  Thompson developed a model of the atom that was different from Dalton’s simple sphere.  Thompson’s model is referred to as the “plum pudding” model (I think plum pudding is something they ate in 19 th century Britain)  I like to call it the chocolate chip cookie model

11.  Probably the most famous experiment ever conducted in science…  THE GOLD FOIL EXPERIMENT!  Ernest Rutherford used a radioactive source (we will talk more about this later) to shoot a thin piece of gold foil

13.  Most of the atom is empty space  There is a massive, dense area at the center of the atom  The area at the center of the atom is small and positively charged  This positive massive region would become known as the nucleus

14.  It did not account for all the mass of the atom  Did not allow us to see that all atoms of the same element are not necessarily exactly alike