2. The History of the Atom

4. Laws which caused doubt in Aristotle ’s Theory

5. #1 Law of Conservation -matter can neither be created nor destroyed in ordinary chemical reactions.(Developed by Antoine Lavoisier) I developed this law a few years before I lost my head on the guillotine

6. #2 Law of Definite Composition -compounds contain the same percentage by mass of each element no matter what the source of the compound. (Developed by Joseph Proust) It ’s all the same to me.

7. #3 Law of Multiple Proportions -elements can combine in more than one ratio to form more than one compound. (Developed by John Dalton) Flexibility is a good thing. Examples H 2 O and H 2 O 2 Water and Hydrogen Peroxide CO and CO 2 Carbon monoxide and Carbon dioxide

8. These questions lead John Dalton to reject Aristotle ’s theory and create a theory of his own.

10. The result of this Theory was the creation of Dalton ’s Model of the atom. Solid indestructable sphere.

11. Discovery of the Sub-atomic Particles

13. Thomson ’s Model of the Atom Represents negative electrons dispersed in positive surroundings.

15. Rutherford ’s Model of the Atom Electron traveling on a curved path around the nucleus. Small dense positively charged nucleus. The gold foil experiment determined that atoms are mainly empty space.

18. In the Bohr model of the atom, electrons can travel only on certain paths which are stable and do not lose energy. Bohr even calculated how many electrons could travel each path in his model. The formula used to calculate the number of electrons on each level was #e - = 2n 2 Where n represents the energy level number. Example: Energy level #3 #e - =2(3) 2 = 18

21. The Current Model of the Atom These all fit together to form the current model of the atom. “ s” orbital “ p” orbital

22. The Quantum Mechanical Model

23. The End