1. Chapter 3 Atoms and Moles

2. Atomic Models

3. 3.1 Matter Made of Atoms  Atomic Theory  Mikhail Lomonosov (1711-1795) and Antoine Lavosier (1743- 1794): developed law of conservation of mass  states that mass of reactants equals mass of products

4. Law of Conservation of Mass

6. 3.1 Matter Made of Atoms  Atomic Theory  Joseph Proust (1754-1826): proposed law of definite proportions  states that two samples of a given compound are made of the same elements in exactly the same proportions by mass

7. 3.1 Matter Made of Atoms  Atomic Theory  Claude-Louise Berthollet (1748- 1822): proposed law of multiple proportions  states that when two elements combine to form two or more compounds, the mass of one element that combines with a mass of the other is in the ratio of small whole #’s

8. 3.1 Matter Made of Atoms  Dalton’s Atomic Theory  John Dalton (1766-1844): developed a new atomic theory  1. all matter is made of atoms, which cannot be subdivided, created, or destroyed  2. atoms of a given element are identical in their chemical and physical properties

9. 3.1 Matter Made of Atoms  Dalton’s Atomic Theory  3. atoms of different elements differ in their physical and chemical properties  4. atoms of different elements combine in simple, whole- number ratios to form compounds

10. 3.1 Matter Made of Atoms  Dalton’s Atomic Theory  5. in chemical reactions, atoms are combined, separated, or rearranged but not created, destroyed, or changed

11. 3.1 Matter Made of Atoms  Further Progress  Jons Berzelius (1779-1848)  studied proportions in which elements combine with one another (over 2000)  experimental underpinning of Dalton’s theory  made table of atomic weights  named ‘halogens’

12. 3.1 Matter Made of Atoms  Further Progress  Jons Berzelius (1779-1848)  invented alphabetical nomenclature of elements  coined terms ‘organic chemistry’, ‘catalysis’, and ‘protein’

13. 3.1 Matter Made of Atoms  Further Progress  valency and bonding described in 1850’s  Stanislao Cannizzaro (remember?): distinction between atoms and molecules  periodic table developed in 1860’s

14. 3.2 Structure of Atoms  Subatomic Particles  Heinrich Geissler (1814-1879): invented the vacuum tube (late 1850’s)  vacuum tube: hollow, glass tube in which the air has been removed; electrodes at either end  produces a glow when current flows between electrodes

15. 3.2 Structure of Atoms  Subatomic Particles  Eugen Goldstein (1850-1930)  named glowing rays ‘cathode rays’ (1876)  showed that they were deflected by magnetic fields; could cast shadows  discovered rays coming from anode; called them ‘canal rays’ (1886)

16. 3.2 Structure of Atoms  Subatomic Particles  William Crookes (1832-1919)  showed that cathode rays were made of particles, not light (1879)  convincing to the British, but not mainlanders

17. 3.2 Structure of Atoms  Subatomic Particles  J. J. Thomson (1856-1940): showed that rays were slower than light (1894)  Jean Perrin (1870-1942): showed that metal plates hit by rays became negatively charged (1895)

18. Three Random Walks

19. 3.2 Structure of Atoms  Subatomic Particles  J. J. Thomson (again)  measured mass/charge; found that particles were small or charge was large (1897)  measured electric charge itself; found electrons to be 1/2000 mass of a H atom (1899)  new atomic model

20. Deflections of Cathode Rays

21. Thomson’s Atomic Model

22. 3.2 Structure of Atoms  Subatomic Particles  Ernest Rutherford (1871-1937)  discovered  and  radiation (1890’s)  discovered  radiation (1900)  discovered that  particles are a He nucleus (1908)

23. , ,  Radiation

24.  Radiation Image

25. 3.2 Structure of Atoms  Subatomic Particles  Ernest Rutherford (1871-1937)  gold foil experiment (1909)   particles fired at gold foil  most went through, some deflected  conclusion: most of the mass and charge of an atom is in the nucleus; electrons in cloud

26. Gold

27. Gold Foil Experiment

28. Expectations versus Reality

29. Explanation

31. Rutherford’s Paper

32. 3.2 Structure of Atoms  Subatomic Particles  Francis Aston (1877-1945): showed that atoms come in different varieties (different weights) (1912)  called isotopes: atoms with the same number of protons but different numbers of neutrons  E.R. discovered proton (1918)

33. Evidence for Isotopes

34. 3.2 Structure of Atoms  Subatomic Particles  James Chadwick (1891-1974): discovered the neutron (sort of) (1932)

35. 3.3 Electron Configuration  Electrons and Light  Light as a moving wave  c = f  c  speed of light = 3 x 10 8 m/s   wavelength (m)  distance between peak or troughs of a wave  f  frequency (1/s  1 hertz)  # of waves per second

36. Waves

37. Light Waves

38. Light

39. 3.3 Electron Configuration  Electrons and Light  Albert Einstein (1879-1955)  atoms emit or absorb EM radiation in discrete (quantized) units (1905)  light has properties of waves and particles (1905)

40. 3.3 Electron Configuration  Electrons and Light  Niels Bohr (1885-1962)  worked with Rutherford  new atomic model: electrons orbit nucleus at particular energy levels (1912)  electrons don’t give off energy (no spiraling allowed)  Why don’t electrons go straight to the nucleus???

41. 3.3 Electron Configuration  Electrons and Light  Bohr’s model  electron in state of lowest possible energy is in ground state  if electron gains energy, it moves to an excited state(!)  if electron falls back to ground state, it releases energy as light

42. Excited State

43. Absorbance and Emission

45. Quantization

46. 3.3 Electron Configuration  Electrons and Light  Bohr’s model, continued  Bohr predicted the wavelengths of light for hydrogen—he was right!  all light wavelengths together are called line-emission spectrum  each element has its own

47. Hydrogen Emission

48. H Absorbance and Emission

49. 3.3 Electron Configuration  Electrons and Light  Louis de Broglie (1892-1987)  particles can be described as waves (1925)  therefore, electrons can only have certain frequencies (energy levels) and can’t fall toward nucleus  quantum atomic model

50. 3.3 Electron Configuration  Quantum numbers  n  principal (main energy levels)  l  angular momentum (shape or type of sublevel)  l = 0  s orbital  l = 1  p orbital  l = 2  d orbital  l = 3  f orbital

51. Principal Quantum Number

52. Energy Level Transitions

53. 3.3 Electron Configuration  Quantum numbers  m l  magnetic (subset of l quantum number)  m s  spin (orientation of magnetic field) +1/2 or -1/2

54. Quantum Numbers

55. Orbital Shapes

56. 3.3 Electron Configuration  Electron Configurations  Pauli exclusion principle: each orbital can hold no more than two electrons  no two electrons can have the same four quantum numbers  Aufbau principle: electrons fill orbitals that have the lowest energy first  1s<2s<2p<3s<3p<4s<3d

57. Overlapping Orbital Energies

58. 3.3 Electron Configuration  Electron Configurations  Hund’s rule: orbitals of the same n and l number are occupied by one electron before pairing occurs

59. Hund’s Rule