1. Discussion: Three Atomic Models of the Atom

2. Some people believe that theories never change. That isn’t true. Theories change until we get it right. The atomic theory is an example.

3. The first atomic theory was named after John Dalton. The atomic theory is at least 3000 years old but John Dalton was the first to develop a modern theory based on scientific evidence. But what did it say? Turn to page 52

4. Dalton’s Atomic Theory 1808 1. Elements are made of tiny particles called ___ 2. All atoms of a given element are ________ 3. The atoms of a given element are different from ______

5. Dalton’s Atomic Theory 4. Atoms of one element can combine with atoms of other elements to form compounds. 5. Atoms are indivisible in chemical processes.

6. WeberTube - Discovery of the electron

7. Thompson’s Model or the Plumb Pudding Model After watching the video on the cathode ray tube, describe the Plumb Pudding model of the atom

9. The Atom Can be Divided The atom contains electrons, protons and neutrons which are called subatomic particles. JJ Thompson discovered the electron. With this discovery, it was known that the atom is divisible and that #5 was wrong. 5. Atoms are indivisible in chemical processes.

10. Rutherford’s Gold Foil Experiment Video

11. Rutherford’s Model

12. The Setup for the Rutherford Model Lead Box

13. The Atom is Mostly Empty Space

15. The Nucleus A very small very dense core of the atom. It contains positively charged protons and neutrally charged neutrons

16. Protons and Neutrons Protons are positively charged particles in the nucleus. The neutron is also in the nucleus but it has no charge Both the proton and neutron are very dense. Almost all of the mass of the atom is contained in the nucleus.

17. Comparing the mass of an Electron to the Proton

18. Comparing The Mass of an Electron to the mass of a Neutron

19. Proton and Neutron