1. Atomic Structure

2.  Democritus and Aristotle ◦ Democritus thought all matter consisted of extremely tiny particles that could not be divided. (Cut aluminum foil in half) ◦ Also thought matter in liquids was round and smooth; in solids rough and prickly ◦ Aristotle thought there was no limit to the number of times matter could be divided.

3.  Developed a theory to explain why the elements in a compound always behave in the same way.  Main Points ◦ 1) All elements are composed of atoms. ◦ 2) All atoms of the same element have the same mass, and atoms of different elements have different masses. ◦ 3) Compounds contain atoms of more than one element. ◦ 4) In a compound, atoms of different elements always combine in the same way.

4.  Used a cathode ray tube to show evidence for subatomic, charged particles.

5.  Plum pudding model (chocolate chip ice cream.  Negatively charged particles evenly spaced throughout a solid mass of positive charge.

6.  The Gold Foil Experiment – Evidence for a nucleus.

7. “Structure of the Atom”

8. A. An atom 1. smallest part of matter 2. Ripping paper example B. Areas of an atom 1. Nucleus – center of an atom -holds protons and neutrons a. Protons (P) – positively charged particle found in the nucleus. -has a mass of 1 -has a charge of 1+

9. b. Neutrons (N) – non-charged particle found in the nucleus. -has a mass of 1 -has no charge “0” 2. Electron Cloud – area around the nucleus which contains electrons a. Electrons (e) – negatively charged particle found outside of the nucleus -has a mass of 0 -has a charge of 1- -moves around the outside of the nucleus

10. Protons Electrons Neutrons

11. ParticleMassChargeLocation of particle Particles in an Atom Review Proton Neutron Electron 1 1 0 1+ 0 1- nucleus Electron cloud

12. A. Def – the # of protons in an atom’s nucleus. 1. Every carbon atom has 6 protons… 2. Every neon atom has 10 protons… B. On P.T. – located right above the chemical symbol *Protons dictate the type of element we have* *Electrons always equal the # of protons*

14. A. Def – The sum of protons and neutrons in the nucleus of an atom. 1. On P.T. – bottom number -round up/down 2. Ex: What is the mass number of the following elements? CarbonOxygen IronCalcium SodiumZinc 12 56 23 16 40 65

15. 3. Mass # = Protons + Neutrons 4. How many Neutrons on average are found in the following elements? BoronFluorine SiliconCopper SilverGold 118 14 6 61 10 35

16. A. Def – An atom that has a different number of neutrons. 1. Does not affect the element 2. Only changes the weight of the element 3. Ex: Boron-10 and Boron-11 p p p p p n n n n n n 5 protons 5 neutrons6 neutrons This means the mass # Boron-10Boron-11

17. 4. How many neutrons do the following isotopes have? Oxygen-14 Titanium-50 Magnesium-22 Potassium-43 Aluminum-23 Iodine-130 6 28 10 24 10 77

18. A. Def – average mass of all isotopes of one element combined. 1. Found on P.T. underneath chemical symbol. 2. Ex: Carbon = 12.011 “Carbon has 3 known isotopes. Carbon-12, 13, and 14. Carbon-12 makes up 99% of all carbon on earth. Carbon-13 and 14 make up 1%.”

19. “Modern Atomic Theory” Chemistry Timeline…pg. 114-115

20. A. Def – a specific area where an electron is likely to be. nucleus 2 electrons 8 electrons 18 electrons 32 electrons e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e- e- e- e- e- e- e- e- e- e-

21. Energy LevelMaximum # of Electrons 1 2 3 4 2 8 18 32

22. 1. Draw a picture of the following atoms with the correct number of e’s, p’s, and n’s… a. Nad. He b. Ale. C c. Kf. S 2. Assign: Read pg. 118 and 119 3. What is the difference between a ground state and an excited state?