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Chapter 5 Early Atomic Theory and Structure

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Democritus of Abdera ... Opposed ideas of Democritus. Empedoclean theory. 4 ... Prime source for ideas of Leucippus and Democritus. Atomism in the Renaissance ... – PowerPoint PPT presentation

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Title: Chapter 5 Early Atomic Theory and Structure


1
Chapter 5Early Atomic Theory and Structure
  • The History of the Atom

2
Objectives
  • History of Atomic Theory (5.1-5.5, 5.7)
  • Subatomic Particles (5.5, 5.8)
  • Atomic Numbers (5.9)
  • Isotopes (5.10)
  • Atomic Mass (5.11)

3
Democritus of Abdera
  • 460 BC to 370 BC
  • World made of empty space and tiny particles
    called atoms
  • Student of Leucippus

4
Democritus of Abdera
  • All matter is composed of atoms, which are bits
    of matter too small to be seen. These atoms
    CANNOT be further split into smaller portions
  • There is a void, which is empty space between
    atoms
  • Atoms are completely solid
  • Atoms are homogenous, with no internal structure
  • Atoms differ in size, shape and weight

5
Aristotle
  • Opposed ideas of Democritus
  • Empedoclean theory
  • 4 elements
  • Earth, air, fire, water
  • Ideas dominate into 17th century

6
Atomism in Antiquity
  • Church spoke against atoms
  • Did not support God creating earth

7
Atomism in the Middle Ages
  • Artistotles works rediscovered (1200s)
  • Catholic Church
  • Atomic thinking Godlessness
  • De Rerum Natura rediscovered in 1417
  • Prime source for ideas of Leucippus and Democritus

8
Atomism in the Renaissance
  • Dominated by Alchemists
  • Mystics, fakes
  • Turning cheap metal into gold
  • Discovery of many elements
  • Preparation of mineral acids

9
Robert Boyle (1627-1691)
  • Matter is divided into little particles of
    several sizes (corpuscles)
  • First to perform truly quantitative experiments
  • Pressure and volume of air

10
Antoine Laurent LavoisierFather of Chemistry
  • 1743-1794
  • Matter can be changed but never created or
    destroyed
  • Law of Conservation of Mass

11
Antoine Laurent LavoisierFather of Chemistry


"It took them only an instant to cut off that
head, and a hundred years may not produce another
like it."




12
Amadeo Avogadro

  • (1776-1856)
  • Equal volumes of gases, under the same
    conditions, have the same number of molecules





13
John Dalton

  • (1766-1844)
  • Englishman
  • School teacher
  • Developed atomic theory





14
John Dalton

  • All matter is composed of atoms
  • Atoms of the same element are identical
  • Atoms cannot be subdivided, created or destroyed





15
John Dalton


4. Atoms of different elements combine in small
whole numbers 5. In chemical reactions, atoms are
combined, separated or rearranged




16
John Dalton


Law of Multiple Proportions When two elements
form a series of compounds, the ratios of the
masses of the second element that combine with 1
gram of the first element can always be reduced
to small whole numbers CO, CO2, CO3, etc.




17
J. J. Thomson

  • 1856-1940
  • Showed experimentally the existence of the
    electron



18
J. J. Thomson

  • Cathode Tube Experiment




19
J. J. Thomson





20
Robert A. Millikan

  • Determined charge of an electron
  • Negative




21
Ernest Rutherford

  • 1871-1937
  • Defined radioactivity
  • Named alpha and beta particles




22
Ernest Rutherford





23
Ernest Rutherford





24
The Modern Day Atom
  • Nucleus
  • Positively charged protons
  • Neutral neutrons
  • Orbiting Nucleus
  • Negatively charged electrons





25
Atomic Numbers (Z)
  • Equal to number of protons in the nucleus
  • NEVER CHANGES





26
Mass Number (A)
  • Sum of protons and neutrons in the nucleus





27
Isotopes of the Elements
  • Same atomic number but different atomic masses
  • Different number of neutrons





28
Ions of the Elements
  • Same number of protons and neutrons
  • Has lost or gained electrons
  • Contains charge




29
Atomic Mass
  • Measured in atomic mass units
  • Equal to exactly 1/12 mass of a carbon-12 atom
  • Average relative mass of the isotopes of that
    element compared to the atomic mass of carbon-12
  • Average atomic mass (seen on periodic table)
  • Atomic mass of each isotope x fraction present
  • Add all.
  • See pg 95




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