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

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

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

4. 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.

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

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

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

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

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

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

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

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

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

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

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

16. I. Structure of the Atom Chemical Symbols Subatomic Particles
Ch Atomic Structure
I. Structure of the Atom
Chemical Symbols
Subatomic Particles

17. 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.

18. 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...

19. B. Subatomic Particles Quarks 6 types 3 quarks = 1 proton or 1 neutronHe
3 quarks = 1 proton or 1 neutron

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

21. A. Orbital
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.

22. A. Orbital
Orbitals have different shapes.

23. 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.

24. 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-

25. C. Bohr Model Activity Choose a number between 1 & 18.
Find your element by the atomic number you picked.
Draw a Bohr Model diagram for your element on your paper.
Round off the mass listed on the table and subtract the atomic # to find the # of neutrons.
Abbreviate the # of ‘p’ and ‘n’ in the nucleus.
Have a partner check your drawing.
Repeat with a new element.

26. III. Masses of Atoms Atomic Mass Mass Number Isotopes
Ch Atomic Structure
III. Masses of Atoms
Atomic Mass
Mass Number
Isotopes

27. A. Atomic Mass atomic mass unit (u) 1 u = 1/12 the mass of a 12C atom
1 proton = 1 u 1 neutron = 1 u
1 u = 1.67  g
© Addison-Wesley Publishing Company, Inc.

28. B. Mass 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 #

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

30. C. Isotopes
© Addison-Wesley Publishing Company, Inc.

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

32. 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

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

34. 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.

35. 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.

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

37. A. Metallic Character
Metals
Nonmetals
Metalloids

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

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

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

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

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

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

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

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

46. 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

47. 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

48. 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

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