Atomic Structure

1. Atomic Structure Daniel R. Barnes Init: sometime about a year before 10/4/2006

2. SWBAT . . . . . . describe what atoms are made of, in terms of size, mass, electric charge, location, and motion. “SWBAT = “Students will be able to”

3. SWBAT . . . . . . explain how theories and laws evolve over time. “SWBAT = “Students will be able to”

4. Click the link! http://scaleofuniverse.com/ When you click the link above and play with the slider on the scale of the universe thingie, make sure to go all the way down to the size of molecules, atoms, the nucleus, and individual protons, neutrons and electrons. You really need to see just how small that stuff is. Thank you, Francisco Lerma and Aranza Guzman for helping me fix the link! DRB 9/8/2014

5. * What is matter? Anything that takes up space and has mass. Solids, liquids and gases. *ORDINARY matter, not dark matter or dark energy.

6. What is matter made of?

7. MATTER is made of ATOMS

8. If matter is made of atoms . . . What are atoms made of?

9. Atoms are made of . . .

10. Atoms are made of . . . Subatomic Particles Subatomic Particles

11. 10 9 8 7 6 5 4 3 2 1 0 -1 -2 -3 -4 -5 -6 -7 -8 -9 -10 Subatomic Particles What does “subatomic” mean? “Sub-” means “below” or “under”. When you start giving number values to altitude, whether you’re talking about airplane altitude or the number of the floor in a building, “under” starts to mean . . . “less than”. On the vertical number line to the right, “2” is below “3” because 2 is less than 3. A subatomic particle is a speck of matter that is less than an atom. A submarine goes underwater.

12. 10 9 8 7 6 5 4 3 2 1 0 -1 -2 -3 -4 -5 -6 -7 -8 -9 -10 10 9 8 7 6 5 4 3 2 1 0 -1 -2 -3 -4 -5 -6 -7 -8 -9 -10 Subatomic Particles What does “subatomic” mean? “Sub-” means “below” or “under”. If the number line to the right were a thermometer, temperatures below zero would be called . . . . . . “sub-zero” temperatures. “Sub-zero” is below zero. “Sub-zero” is less than zero.

13. Subatomic Particles What does “subatomic” mean? A “subatomic particle” is less than an atom. A “subatomic particle” is just a part of an atom. There are three subatomic particles you have to get to know . . .

14. Subatomic Particles proton mass = 1.007 amu charge = + 1 mass = 1.009 amu neutron charge = 0 = “neutral” mass = 0.000549 amu electron charge = -1

15. Electrostatic Forces

16. Electrostatic Forces You’re repulsive! You’re rePULsive! ? repulsion ? repulsion ? attraction

17. Electrostatic Forces ? no reaction ? no reaction * Bringing a charged object near a neutral object can cause the neutral object to develop + & - zones, which can make the neutral object attracted to - & + objects, so my jury is not yet out on neutrons . . . ? no reaction

18. Electrostatic Forces

19. Which two particles are the heaviest? proton mass = 1.007 amu mass = 1.007 amu charge = + 1 mass = 1.009 amu neutron mass = 1.009 amu charge = 0 = “neutral” mass = 0.000549 amu mass = 0.000549 amu electron charge = -1

20. Historical Trivia Time!

21. Who discovered the electron? Joseph John Thomson, 1897 He didn’t do all the work, though.

22. Crookes tube William Crookes 1832-1919

23. magnet NOTE: A normal dry cell (“battery”) only provides 1.5 volts. This experiment required thousands of volts.

24. Electron momentum or radiometric effect?

25. This is more or less a picture of Thomson’s “plum pudding” model of the atom. It’s an improvement over Democritus’ and Dalton’s models in that it states that an atom CAN be broken into pieces.

26. Who discovered the nucleus? Ernest Rutherford, 1911

27. 1909 omfg! Hans Geiger Ernest Marsden ZnS

28. Imagine a marble on the 50-yard line. That’s how small the nucleus of an atom is compared to the atom as a whole.

29. This cartoon drawing of an atom is largely based on the “solar system” model of the atom that Rutherford came up with after the gold foil experiment. It’s full of flaws, but it was an improvement on Thomson’s “plum pudding” model.

30. Note that the nucleus in this cartoon is shown as being far too . . . BIG. (Remember the marble on the 50 yard line!)

31. Materials reminder: Got graph paper? You’ll need it next week

32. real rabbit cartoon rabbit

33. real atoms (same picture as page 103 in section 4.1 of your book) cartoon atom

34. ? ? ? ? ? ? Cartoon electron orbit More realistic electron orbit

35. nucleus

36. So, what’s wrong with the way I drew this atom? The nucleus is far too large. Let’s shrink it. Is that small enough? Okay. Let’s shrink it again, then.

37. Is that small enough for you? An atom may be tiny, but it’s gigantic compared to the nucleus in its center. Let’s shrink it again, then. Empty space Okay. Is THAT small enough? That’s pretty strange, considering that the nucleus is where over 99% of the atom’s mass is. Why not? Yep. If you can see it, I drew it too big. Atoms are made mostly of . . .

38. Is that small enough for you? An atom may be tiny, but it’s gigantic compared to the nucleus in its center. Let’s shrink it again, then. Empty space Okay. Is THAT small enough? That’s pretty strange, considering that the nucleus is where over 99% of the atom’s mass is. Why not? Yep. If you can see it, I drew it too big. Atoms are made mostly of . . .

39. Empty space And you’re made of atoms, so . . .

40. Hey, Mr. Barnes! I got a question! . . . YOU’RE made mostly of empty space.

41. If I’m made mostly of empty space, And you’re made mostly of empty space . . .

42. How come it hurts so bad when I kick you in the nuts?

43. Since we’re made mostly of empty space, you’d think we’d just pass through each other like ghosts. Instead, we bounce off of each other like billiard balls. Why is that?

44. Ask me again when we’ve done the static electricity lab. Okay. Can we go to the “Did you get it” questions, then? We HAVE done the static electricity lab! Explain! Explain!

45. Do you remember what happened when we charged up both balloons and tried to bring them close together? Think about that for a bit while we imagine me kicking a wall.

46. An atom in the wall An atom in my foot As my foot gets closer and closer to the wall, what parts of the atoms come into contact first? The electrons are on the outside of the atom, so they’re the parts that come closest together. The electrons are the ambassdors of an atom. Let’s forget about the atoms and just focus on the electrons.

47. Yes we do, and you just hurt mine! I don’t care if you’re sorry. You’re gonna hear from my lawyer! An electron in the wall An electron in my foot How do electrons feel about each other? They’re both negatively-charged, so . . . Well, okay, they repel each other. Electrons don’t really have feelings. They hate each other. So, anyway, electrons push each other away. They feel an “electrostatic repulsion” for each other.

48. An electron in the wall An electron in my foot In order for my foot to get closer to the wall, I have to exert force to get my electrons to get closer to its electrons. The force my muscles exert has to be at least as strong as the repulsion between our electrons.

49. An electron in the wall An electron in my foot Charge on the first object Charge on the other object There’s an equation that predicts the electrical force between two charged objects. It looks a lot like Newton’s law of universal gravitiation. kQ1Q2 Fe = R2 Electrostatic Force Distance between the two objects

50. According to the equation, if the charge of either particle gets larger, the force gets larger also. An electron in the wall An electron in my foot ( ) When the numbers on the top of a fraction get larger, the value of the fraction gets larger. kQ1Q2 Fe = R2