1. Chapter 3 Atomic Theory

2. Early Theories 4 elements

3. Democritus (460 - 370 BC) Greek philosopher Atomos – indivisible particles Atoms are the smallest particle that retains the chemical identity

4. The Greeks Used Logic The Greeks also believed in a combination of elements to make new things. For example: Water and Earth = Mud Mud might just seem like a nuisance to us, but back then it was a building material. Fire and Earth made Lava. If you are curious check out the Little Alchemy app (game) that can be found in Google Apps. It is a fun game.

5. Jabir Ibn Haiyan (700? - 803 AD) Father of Chemistry Practiced Alchemy Discovered metals

6. Antoine Lavoisier (1743 - 1794) Law of Conservation of Matter

7. Joseph Louis Proust (1754-1826) Law of Constant Composition

8. John Dalton (1766 - 1844) Atomic Theory This was the true start of our modern theory of matter.

10. Dalton’s Theory Dalton’s ideas were a good start. However, we need to look at one of his postulates more closely. He stated that “All atoms of the same atom are identical…” He didn’t know about isotopes. The neutron wasn’t discovered for another 130 years.

11. Atomic Theory Elements made of atoms Atoms are identical of a given type of element Atoms neither created nor destroyed Compounds have fixed ratio of atoms

12. Ben Franklin (1706-1790) Two types of charge positive (+) and negative (-)

13. Michael Faraday (1791-1867) Atoms are related to electricity

14. J.J. Thomson (1856 - 1940) Cathode Ray Tube (CRT) stream of electrons Plum Pudding Model

15. cathode ray tube

17. Thomson’s Model This lead directly to the idea of electrons and was a major advancement in atomic theory. Sometimes this theory is called “Raisins in a Plum Pudding.”

18. Robert Millikan (1838-1953) Determined charge & mass of electron

20. Henri Becquerel (1852 - 1908) Uranium exposes film

21. Marie (1867-1934) & Pierre Curie (1859-1906) Discovered radioactivity elements Radioactive decay

22. Earnest Rutherford (1871 - 1937) Discovered radioactivity particles Discovered Nucleus Solar system model of atom

23. Discovery of particles

24. gold foil experiment

25. Rutherford’s Gold Foil Experiment There are animations on the website so that you can get a better visual of the experiment. Rutherford’s experiment was truly a marvel. It answered a lot of questions and gave a good framework for future investigations. Remember that it was still a theory – there is a long way to go in understanding an atom.

26. Early Atomic Theory At this point, this completes our look at the early contributors into Atomic Theory and Structure. You were given a lot of names, but here are the ones I want you to focus on: Democritus, Dalton, Thompson, Rutherford When we get to other topics, we will explore a few more of them in detail such as Becquerel and the Curies.

27. Study Guide Help To assist you in your preparation, take note that I will not be asking much if anything about the following scientists: Ben Franklin, Joseph Proust, Michael Faraday Robert Millikan, Jabir Ibn Haiyan, and Antoine Lavoisier might get a short question or two on a test or quiz.

28. Niels Bohr (1885 – 1962) Electrons do not orbit like planets Described shells or energy levels Quantum theory

29. H.G.J. Moseley (1887 - 1915) Discovered protons (+) in the nucleus Rearranged periodic table

30. Sir James Chadwick (1891-1974) Discovered neutrons (0) in the nucleus

31. Quarks, Quarks, Quarks (1950s – present) 6 quarks have been discovered that make up protons and neutrons

33. Protons Make up the nucleus Charge +1.602 x 10 -19 C Mass = 1.673 x 10 -24 g Charge +1 Mass = 1 amu

34. Neutrons Make up the nucleus Charge 0 Mass = 1.675 x 10 -24 g Mass = 1 amu

36. Electrons Occur in electron Clouds Charge -1.602 x 10 -19 C Mass = 9.109 x 10 -28 g Charge = -1 Mass = 0 amu

37. Atoms are small but nuclei are smaller Diameter of a penny has 810 million copper atoms

38. Atomic Number Number of protons in an atom Electrically neutral atoms have the same number of electrons as protons Ions are formed by gaining or losing electrons

39. Isotopes Same number of Protons but different numbers of neutrons Mass number is the sum of the protons and the neutrons Isotopes have the same chemical properties Violates Dalton’s atomic theory

41. Masses of Atoms 1 amu = 1/12 mass of a 12 C atom 99% Carbon 12 C 1% Carbon 13 C Average atomic mass of C is 12.01 amu Mass number is for one atom Listed as a decimal on the periodic table

43. Nuclear Symbol

45. Nuclear Reactions Nuclear reactions involve the nucleus of the atom Radioactivity is the spontaneous emission of radiation from an atom Nuclear reactions change elements involved

46. Alpha Particle Alpha particle –Helium nucleus with no electrons –Will bounce off of paper and skin –+2 charge

48. Beta Particle Beta particle –High energy electron –Come from the decay of a neutrons –Will penetrate skin –Blocked by aluminum and Plexiglass –-1 charge

50. Gamma Rays –High energy wave –No charge –No mass –Penetrates skin, damages cells and mutates DNA –Blocked by lead Gamma Radiation

52. Nuclear Stability Most elements have a stable nucleus A strong nuclear force holds protons and neutrons together Neutrons act as the “glue” holding the protons together

54. Nuclear Equations Scientists use a nuclear equation when describing radioactive decay The mass number and atomic number must add up to be the same on both sides of the equation

55. Beta Decay Beta decay results in an increase in the atomic number

56. Practice Write the nuclear equation of the alpha decay of Radon – 226 Write the nuclear equation of the alpha decay of Gold - 185

57. Practice Write the nuclear equation of the beta decay of Iodine - 131 Write the nuclear equation of the beta decay of Sodium - 24

58. Chapter 24 Applications of Nuclear Chemistry

59. Half Life Radioisotopes are radioactive isotopes of elements (not all isotopes are radioactive) A half-life is the amount of time it takes for one half of a sample to decay. http://lectureonline.cl.msu.edu/~mmp/applist/de cay/decay.htmhttp://lectureonline.cl.msu.edu/~mmp/applist/de cay/decay.htm

60. Beta Decay of Phosphorous - 32

61. Radiocarbon Dating Carbon - 14 undergoes beta decay Half life of 5,730 years Used to approximate ages 100 – 30,000 years Other radioisotopes are used to measure longer periods of time

62. ParentDaughterHalf Change in... Carbon-14 Nitrogen-145730 years Uranium-235Lead-207704 million years Uranium-238Lead-2064,470 million years Potassium-40Argon-401,280 million years Thorium-232Lead-20814,010 million years Rubidium-87Strontium-8748,800 million years

63. Nuclear Bombardment Nuclear scientists make nuclei unstable by being bombarded with particles Also known as particle accelerators or “atom smashers”

66. Radiation SI units are in Curies (Ci) One Curies is amount of nuclear disintegrations per second from one gram of radium Also measured in rem (Roentgen equivalent for man Over 1000 rem is fatal Detected by a Geiger counter

68. Nuclear Power Nuclear Reactors use fission of Uranium-235 as source of energy A large nucleus is split into two smaller nuclei A small amount of mass is converted to a tremendous amount of energy ~1 lb Uranium 235 = 1 million gallons of gasoline http://people.howstuffworks.com/nuclear- power2.htmhttp://people.howstuffworks.com/nuclear- power2.htm

72. Nuclear Fusion 2 atomic nuclei fuse releasing a tremendous amount of energy

74. Nuclear Weapons Source of energy is Plutonium or Hydrogen Can be fusion or fission

75. Gun-triggered fission bomb (Little Boy - Hiroshima), Implosion-triggered fission bomb (Fat Man - Nagasaki), http://people.howstuffworks.com/nuclear-bomb5.htm