2. Chapter 4 Notes (4) Sections 4-1,4-2

3. I.Development of an Atomic Model *Matter: anything that has mass and volume *Indirect Evidence: evidence you get without actually seeing or touching the object

4. -Greek Model (Democritus) *atom: smallest particle of an element that has the prop of the element ~atomos: meaning not to be cut

5. -Dalton ’ s Atomic Theory 1. All elements are composed of atoms 2. Atoms of the same element are exactly alike

6. 3. Atoms of diff. elements are diff. 4. Compounds are formed by joining of atoms of 2 or more elements

7. II. A Divisible Atom -Thomson ’ s Model: ~Plum Pudding *Electrons: - charge

8. -Rutherford ’ s Model ~Gold Foil Experiment ~the atom was mostly empty space with a dense, positively charged nucleus in the center. *Nucleus: the center of the atom

9. -Bohr Model ~electrons move in definite orbits around the nucleus

10. -Wave Model (Today accepted model) ~electrons don ’ t move about in a definite path ~probable location is based on how much nrg the electron has

11. SEE HISTORY OF THE ATOM WEBSITE http://hi.fi.tripod.com/timeline/

12. III. Subatomic Particles *smaller than the atom

13. -Three main subatomic part. 1. proton 2. neutron 3. electron **quarks (make up 1 & 2)**

14. -Nucleus *center of the atom

15. mass (amu) charge location ~proton:1+nucleus ~neutron: 1+/- nucleus ~electron: 1/1836- e- cloud

16. *Atomic Mass Unit (amu): measures mass of subatomic part. -?? Where does it come from??

17. -Atomic # *number of + in the nucl ~identifies the element ~never chngs

18. - Isotopes *same # of +, but diff # of neutrons EX: -Mass # and Atomic Mass *sum of the + and neutrons in its nucleus

19. *Aver Atomic mass: aver of the masses of all the atoms in the sample. ~mass # - atomic# = #of neutrons

20. III. stop 3 H Nuclear Notation 1 Hydrogen-3 Hyphenated Notation

21. III. continue - Electrons (e-) *e- cloud: place in which e- ’ s are likely to be found ~location depends upon how much nrg the e- has

22. *nrg levels: most likely location of the e- ~2,8,8. *Valence e-: e- outer most nrg level

23. ~Movement of e- ’ s: -in: lose nrg -out: gain nrg

24. IV. Forces Within the Atom Video #14 - The four forces that account for the behavior of sub part 1. electromagnetic force *either attract or repel particles

25. video #15 2. strong force *opposes electromag force of repulsion between + ~only when + are very close together

26. 3. weak force *key to the power of the sun ~responsible for radioactive decay ~ +/- ---> + and -

27. 4. gravity *weakest force known in nature ~force of attraction exerted between all objects