1. Atomic Structure Timeline

2. Democritus (400 B.C.)
Proposed that matter was composed of tiny indivisible particles
Not based on experimental data
Greek: atomos

3. Alchemy (next 2000 years) Mixture of science and mysticism.
Lab procedures were developed, but alchemists did not perform controlled experiments like true scientists.

4. John Dalton (1807) British Schoolteacher Billiard Ball Model
based his theory on others’ experimental data
Billiard Ball Model
atom is a uniform, solid sphere

5. John Dalton Dalton’s Four Postulates
1. Elements are composed of small indivisible particles called atoms.
2. Atoms of the same element are identical. Atoms of different elements are different.
3. Atoms of different elements combine together in simple proportions to create a compound.
4. In a chemical reaction, atoms are rearranged, but not changed.

6. Henri Becquerel (1896) Discovered radioactivity Three types:
spontaneous emission of radiation from the nucleus
Three types:
alpha () - positive
beta () - negative
gamma () - neutral

7. J. J. Thomson (1903) Cathode Ray Tube Experiments Discovered Electrons
beam of negative particles
Discovered Electrons
negative particles within the atom
Plum-pudding Model

8. J. J. Thomson (1903) Plum-pudding Model
positive sphere (pudding) with negative electrons (plums) dispersed throughout

9. Ernest Rutherford (1911) Gold Foil Experiment Discovered the nucleus
dense, positive charge in the center of the atom
Nuclear Model

10. Gold Foil Experiment
Alpha particles shot through gold foil. Most went straight through. A few were deflected because the particle hit the nucleus of the gold foil.

11. Ernest Rutherford (1911) Nuclear Model
dense, positive nucleus surrounded by negative electrons

12. Niels Bohr (1913) Bright-Line Spectrum Energy Levels Planetary Model
tried to explain presence of specific colors in hydrogen’s spectrum
Energy Levels
electrons can only exist in specific energy states
Planetary Model

13. Niels Bohr (1913) Bright-line spectrum Planetary Model
electrons move in circular orbits within specific energy levels

14. Niels Bohr
Brightline spectrum

15. Erwin Schrödinger (1926) Quantum mechanics Electron cloud model
electrons can only exist in specified energy states
Electron cloud model
orbital: region around the nucleus where e- are likely to be found

16. Electron Cloud Model (orbital)
Erwin Schrödinger (1926)
Electron Cloud Model (orbital)
dots represent probability of finding an e- not actual electrons

17. James Chadwick (1932) Discovered neutrons Joliot-Curie Experiments
neutral particles in the nucleus of an atom
Joliot-Curie Experiments
based his theory on their experimental evidence

18. revision of Rutherford’s Nuclear Model
James Chadwick (1932)
Neutron Model
revision of Rutherford’s Nuclear Model

20. Structure of the Atom Chemical Symbols Subatomic Particles
Atomic Structure
Structure of the Atom
Chemical Symbols
Subatomic Particles

21. Metal that forms bright blue solid compounds.
A. Chemical Symbols
Capitals matter!
Element symbols contain ONE capital letter followed by lowercase letter(s) if necessary.
Metal that forms bright blue solid compounds.
Co vs. CO
Poisonous gas.

22. B. Subatomic Particles in a neutral atom Most of the atom’s mass.
NUCLEUS
ELECTRONS
in a neutral atom
PROTONS
NEUTRONS
NEGATIVE CHARGE
POSITIVE CHARGE
NEUTRAL CHARGE
Most of the atom’s mass.
Atomic Number
equals the # of...

23. B. Subatomic Particles 3 quarks = 1 proton or 1 neutron Quarks He
6 types He
3 quarks = 1 proton or 1 neutron

24. II. Electron Cloud Model Orbital Energy Levels Bohr Model Diagrams
Ch Atomic Structure
II. Electron Cloud Model
Orbital
Energy Levels
Bohr Model Diagrams

25. A. Orbital Can’t pinpoint the location of an electron.
Region where there is 90% probability of finding an electron.
Can’t pinpoint the location of an electron.
Density of dots represents degree of probability.

26. A. Orbital
Orbitals have different shapes.

27. B. Energy Levels Electrons can only exist at certain energy levels.
Low energy levels are close to the nucleus.
Each energy level (n) can hold 2n2 electrons.

28. C. Bohr Model Diagrams
Simplified energy levels using Bohr’s idea of circular orbits.
Can replace with: 3p 4n
Lithium
Atomic #: 3
Mass:
# of p: 3
# of e: 3
# of n: 4 e- e- p n
Maximum e-
Level 1 2e-
Level 2 8e-
Level 3 18e-
Level 4 32e- e-

29. III. Masses of Atoms Atomic Mass Mass Number Isotopes
Atomic Structure
III. Masses of Atoms
Atomic Mass
Mass Number
Isotopes

30. A. Atomic Mass 1 proton = 1 u 1 neutron = 1 u 1 u = 1.67  10-24 g
atomic mass unit (u or amu)
1 u = 1/12 the mass of a 12C atom
1 proton = 1 u 1 neutron = 1 u
1 u = 1.67  g
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31. B. Mass Number Always a whole number.
Sum of the protons and neutrons in the nucleus of an atom.
© Addison-Wesley Publishing Company, Inc.
Always a whole number.
# of neutrons = mass # - atomic #

32. C. Isotopes Mass # Atomic # Isotope symbol or Nuclear Symbol:
Atoms of the same element with different numbers of neutrons.
Isotope symbol or Nuclear Symbol:
Mass #
Atomic #
“Carbon-12”

33. Practice
Element Nuclear Hyphen Symbol Notation
Magnesium
Cobalt

34. Practice There are three isotopes of the element carbon: Carbon-12
The numbers 12, 13,14 represent what?

35. C. Isotopes
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36. C. Isotopes Average Atomic Mass reported on Periodic Table
weighted average of all isotopes
Avg.
Atomic
Mass

37. C. Isotopes
EX: About 8 out of 10 chlorine atoms are chlorine-35. Two out of 10 are chlorine-37.
Avg.
Atomic
Mass
35.4 u

38. Families of Elements Elements are classified into three categories
A. Metals
Shiny solids; good conductors of heat and electricity

39. B. Nonmetals
all found on the right side of the periodic table (except for Hydrogen)
Can be solids, liquids, or gases

40. Semiconductors or metalloids
non metals that can conduct heat and electricity

41. I. History of the Periodic Table Mendeleev Mosely
Ch The Periodic Table
I. History of the Periodic Table
Mendeleev
Mosely

42. A. Dmitri Mendeleev Organized elements by increasing atomic mass.
Dmitri Mendeleev (1869, Russian)
Organized elements by increasing atomic mass.
Predicted the existence of undiscovered elements.

43. B. Henry Mosely Organized elements by increasing atomic number.
Henry Mosely (1913, British)
Organized elements by increasing atomic number.
Fixed problems in Mendeleev’s arrangement.

44. II. Organization Metallic Character Rows & Columns Table Sections
Ch The Periodic Table
II. Organization
Metallic Character
Rows & Columns
Table Sections

45. A. Metallic Character
Metals
Nonmetals
Metalloids

46. B. Table Sections Representative Elements Transition Metals
Inner Transition Metals

47. B. Table Sections Overall Configuration Lanthanides - part of period 6
Actinides - part of period 7

48. C. Columns & Rows
Group (Family)
Period

49. III. Periodic Trends Terms Periodic Trends Dot Diagrams
Ch The Periodic Table
III. Periodic Trends
Terms
Periodic Trends
Dot Diagrams

50. A. Terms
Periodic Law
Properties of elements repeat periodically when the elements are arranged by increasing atomic number.

51. A. Terms First Ionization Energy
Valence Electrons
e- in the outermost energy level
First Ionization Energy
energy required to remove an e- from a neutral atom

52. B. Periodic Trends
Atomic Radius
Increases to the LEFT and DOWN.

53. B. Periodic Trends Increases to the RIGHT and UP.
First Ionization Energy
Increases to the RIGHT and UP.

54. Be or Ba Ca or Br Ba Ca B. Periodic Trends
Which atom has the larger radius?
Be or Ba
Ca or Br Ba Ca

55. N or Bi Ba or Ne N Ne B. Periodic Trends
Which atom has the higher 1st I.E.?
N or Bi
Ba or Ne N Ne

56. B. Periodic Trends Group # = # of valence e- (except He)
Families have similar reactivity.
Period # = # of energy levels 1A 2A
3A 4A 5A 6A 7A 8A

57. C. Dot Diagrams
Dots represent the valence e-.
EX: Sodium
EX: Chlorine

58. Families of elements

59. Families of elements Group one: Alkali Metals
- Soft, shiny, reacts violently with water
- Has one valence electron that can be easily removed to form a cation
Example: Sodium ( Na+ )

60. Families of elements Group 2:Alkaline earth metals
- have 2 valence electrons
- do not react as violently
- will give up 2 electrons and make a cation
Example: Calcium ( Ca2+ )

61. Chapter 4: Families of elements

62. Families of elements Group 13 (3A) is the Boron Family
- This group is a mixture of metalloids and metals
-Have 3 valence electrons

63. Families of elements Group 14 (4A) is the Carbon Family
- This group is a mixture of metals, nonmetals and metalloids
- Have 4 valence electrons

64. Families of elements Group 15 (5A) is the Nitrogen Family
- This family is a mixture of metals, nonmetals, and metalloids
- Have 5 valence electrons

65. Families of elements Group 16 (6A) is the Oxygen Family
- This group has 6 valence electrons
- This family is a mixture of metals, nonmetals, and metalloids

66. Families of elements Group 17 (7A) are the Halogens
This group is very reactive.
This group is all nonmetals and has 7 valence electrons.
Nonmetals gain electrons to form negative ions called anions.
Example: Chlorine (Cl- )

67. Families of elements Group 18 (8A) are the Noble Gases
This group has 8 valence electrons
They exist as single atom gases.
They are un-reactive.