1. Atomic Structure and The Periodic Table
Chapter 4
Atomic Structure and The Periodic Table

2. Ancient Greeks

3. Democritus’s Greek Philosopher

4. Democritus’s Atomic Theory
Atoms are indivisible and indestructible.
Each substance had a different type of atom.
Liquid – smooth and round
Solid – rough and prickly

5. Who’s Next?
Late 1700’s - John Dalton- England.
Teacher- summarized results of his experiments and those of others.
Dalton’s Atomic Theory
Combined ideas of elements with that of atoms.

6. John Dalton ( )

7. Dalton’s Atomic Theory
All matter is made of tiny indivisible particles called atoms.
Atoms of the same element are identical, those of different atoms are different.
Atoms of different elements combine in whole number ratios to form compounds.
Chemical reactions involve the rearrangement of atoms. No new atoms are created or destroyed.

8. Just how Small is an Atom?
Think of cutting a piece of lead into smaller and smaller pieces
How far can it be cut?
An atom is the smallest particle of an element that retains the properties of that element

9. J. J. Thomson - English physicist. 1897
Parts of Atoms
J. J. Thomson - English physicist. 1897
Made a piece of equipment called a cathode ray tube.
It is a vacuum tube - all the air has been pumped out.

10. J.J. Thompson (1856 – 1940)

11. Thompson 1897

12. Thomson’s Experiment
Voltage source - +
Vacuum tube
Metal Disks

13. Thomson’s Experiment
Voltage source - +

14. Thomson’s Experiment
Voltage source - +

15. Thomson’s Experiment
Voltage source - +

16. - + Thomson’s Experiment
Voltage source - +
Passing an electric current makes a beam appear to move from the negative to the positive end.

17. Thomson’s Experiment
Voltage source - +
Passing an electric current makes a beam appear to move from the negative to the positive end.

18. Thomson’s Experiment
Voltage source - +
Passing an electric current makes a beam appear to move from the negative to the positive end.

19. Thomson’s Experiment
Voltage source - +
Passing an electric current makes a beam appear to move from the negative to the positive end.

20. By adding an electric field.
Thomson’s Experiment
Voltage source
By adding an electric field.

21. Thomson’s Experiment
Voltage source + -

22. Thomson’s Experiment
Voltage source + -

23. Thomson’s Experiment
Voltage source + -

24. Thomson’s Experiment
Voltage source + -

25. Thomson’s Experiment
Voltage source + -

26. Thomson’s Experiment
Voltage source + -

27. Other particles
Proton - positively charged pieces 1840 times heavier than the electron – by E. Goldstein
Neutron - no charge but the same mass as a proton – by J. Chadwick
Where are the pieces?

28. Ernest Rutherford ( )

29. Rutherford

30. Rutherford’s experiment
Ernest Rutherford -English physicist. (1910)
Plum Pudding model of the atom.
Wanted to see how big they are.
Used radioactivity.
Alpha particles.
Shot them at gold foil.

31. Rutherford’s experiment
When an alpha particle hits a fluorescent screen, it glows.
Here’s what it looked like.

32. Fluorescent
Screen
Lead block
Uranium
Gold Foil

33. What he expected…

34. Because…..

35. He thought the mass was evenly distributed in the atom.

36. Since he thought the mass was evenly distributed in the atom.

37. What he got…

38. + Atom is mostly empty. Small dense, positive piece at center.
How he explained it
Atom is mostly empty.
Small dense, positive piece at center.
Alpha particles are deflected by it if they get close enough. +

39. +

40. Homework 4-1
Worksheet: 4.1 Due: 10/24/08

41. Smaller Particles - Quarks
Tevatron
1.3 miles

42. P
Quarks N
Quarks

43. Section 10-2 Wrap-up Page: 277
Homework 10-2
Section 10-2 Wrap-up Page: 277
Due: 2/14/06

44. Matter and Atoms
Nucleus e- p+
Protons
Electrons n
Neutrons

45. Elements Chemical Symbols Structure of the Atom one type of atom.
Substances made up of only
one type of atom.
Chemical Symbols
A shorthand way to write the
names of the elements.

46. # of protons = # of electrons
Atomic Number
The number of protons
in an atom.
In a neutral atom
# of protons = # of electrons

47. Atomic mass - # of protons
The number of
protons and neutrons
in an atom.
# of neutrons =
Atomic mass - # of protons

48. The average of the atomic mass of all the isotopes of that element.
Average Atomic Mass
The average of the atomic mass
of all the isotopes of that element.

49. Atoms of the same element with different number of neutrons.
Isotopes
Atoms of the same element with different number of neutrons.
1P+ 0N
1e-
Protium
1P+ 2N
1e-
Tritium
1P+ 1N
1e-
Deuterium
Average Atomic Mass for H =

50. Atomic Number (# of Protons)15
Phosphorus P
Symbol
Average Atomic Mass
(31)
Name

51. ) ) ) 2e- 8e- 5e- Element: Phosphorus # of Protons: 15 15p+
# of Neutrons:
31 –15 = 16
16nº
# of Electrons: 15 )
2e- )
8e- )
5e-

52. Homework 4-2
Worksheet: 4-2 Due: 10/24/08

53. Bohr 1913
Planetary Model

54. Energy Levels
The possible energies that an electron in an atom can have are called Energy Levels.

55. Energy Levels
2nd Level
Nucleus
1st Level
3rd Level
4th Level

56. Energy e-
Energy

57. Evidence of Energy levels
The energy given off by an electron is in the form of light.
Specific element give off specific colors.
Spectral Analysis

58. Evidence of Energy levels

59. Electron Cloud Model 1926
nucleus

60. nucleus Electron Cloud Model 1926
Scientist use the electron cloud model to describe the possible locations of electrons around the nucleus.

61. Atomic Orbitals
In each energy level the electrons can have certain orbits that they can take.
This a probability of where the electron can be found.

62. Electron Cloud Model 2nd Level 8e- Nucleus 3rd Level 18e-
1st Level 2e-

63. Maximum Number of Electrons
Atomic Orbitals
Energy
Level
Number of
Orbitals
Maximum Number of Electrons 1 2 4 8 3 9 18 16 32

64. Number of Electrons )
2e- )
8e- )
18e- )
32e-

65. Electron Configuration
Where the electrons are in the orbitals of the atom.
The most stable configuration is the one in which the electrons are in orbitals with the lowest energy.
Lowest Energy of the electrons is called the Ground State.

66. ) ) ) 2e- 8e- 5e- Element: Phosphorus # of Protons: 15 15p+
# of Neutrons:
31 –15 = 16
16nº
# of Electrons: 15 )
2e- )
8e- )
5e-

67. Homework 4-3
Worksheet: 4-3
Due: 10/28/08
Test: 10/30/08

68. Democritus’s Atomic Theory
Indivisible
Indestructible
Each substance - different type atom.

69. Dalton’s Atomic Theory
Billiard Ball Model

70. Dalton’s Atomic Theory
Indivisible particles called atoms.
Same elements - identical atoms.
Whole number ratios - compounds CO2 CO
Chemical reactions … … rearrangement of atoms.

71. Existence of Charged Particle
Thomson’s Experiment
Voltage source + -
Existence of Charged Particle
Positive and Negative

72. Plum Pudding Model

73. Rutherford’s Experiment+

74. Small dense, + piece at center.
Atoms have: +
Mostly empty.
Small dense, + piece at center.

75. Electrons in Energy Levels
Planetary Model
Bohr
Electrons in Energy Levels

76. Electron Cloud Model
nucleus

77. Matter and Atoms
Nucleus e- p+
Protons
Electrons n0
Neutrons

78. Atomic Number (# of Protons)14 Si
p+ = 14
e- = p+ = 14
n0 = Mass - p+ n0 = 27 – 14 = 13
26.982
Average Atomic Mass
(p+ + n0 = 27)
AKA - Mass Number
Aluminum

79. p+ = 14
e- = 14
n0 = 13 4 8 2

80. Atomic Orbital
A region of space around the nucleus where an electron is like to be found.
Contains 2 electrons.

81. 4 5 8 7 2 2
Ground
State
Excited
State

82. Atoms of the same element with different number of neutrons.
Isotopes
Atoms of the same element with different number of neutrons.
Cl - 35
Cl - 37
p+ - 17
p+ - 17
n0 - 18
n0 - 20
Average Atomic Mass –

83. Element #2
Element #3
Element #1

84. Element #3: ________________
Color: ____________
Spectrum
Element #4: ________________
Color: ____________
Spectrum