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Bradford Aylin Period 5

Published on Nov 20, 2015

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PRESENTATION OUTLINE

ATOMIC THEORY TIMELINE

KNOWLEDGE OVER TIME
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DEMOCRITUS 400 BC

ATOMIC THEORY
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ATOMOS THEORY

  • Here is Democritus theory that he adopted from Leucippus
  • Atoms are indestructible, are solid but not invisible and are homogenous
  • Atoms differ in size, shape, mass, position, and arrangement
  • All matter consists of invisible particles called atoms
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ARISTOTLE 384 BC

ATOMIC THEORY

EARTH,WIND,FIRE,AND WATER ELEMENTS

  • Aristotle supported and added to the idea that everything was mace up of..
  • 4 elements, earth, wind, fire, and water
  • The elements were "pure" but could not be found in that state on earth.
  • Every visible thing was made up of some combination of earth, water, air, and fire.

JOHN DALTON 1803

ATOMIC THEORY
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BILLIARD BALL MODEL

  • Where Dalton and Democritus would have agreed...
  • is that atoms were the smallest, most basic unit of matter.
  • Where Dalton advanced atomic theory was by saying we had many different atoms out there.
  • His model basically says you can't divide the atom into smaller pieces.

JJ THOMPSON 1897

ATOMIC THEORY

PLUM PUDDING MODEL

  • Thomson originally believed that the hydrogen atom must be made up of more than two thousand electrons
  • Later Thomson suggested that atoms contained far fewer electrons, a # roughly equal to the atomic number.
  • Thomson proposed a 'plum pudding' model...
  • With positive and negative charge filling a sphere only one ten billionth of a metre across.
  • This plum pudding model was generally accepted.

CATHODE RAY EXPERIMENT

  • First experiment was to build a cathode ray tube with a metal cylinder on the end
  • It had two slits in it, leading to electrometers, which could measure small electric charges
  • He found that by applying a magnetic field across the tube.....
  • There was no activity recorded by the electrometers and so the charge had been bent away by the magnet
  • This proved that the negative charge and the ray were inseparable and intertwined.

ERNEST RUTHERFORD 1911

ATOMIC THEORY

POSITIVELY CHARGED NUCLEUS MODEL

  • Rutherford bombarded gold foil with alpha particles
  • A source which undergoes alpha decay is put in a lead box with a hole in it
  • Any of the alpha particles which hit the inside of the box are stopped
  • Only those which pass through the opening are allowed to escape, they follow a straight line to the gold foil
  • The atom is 99.99% empty space. Nucleus contains postitive charge. Nucleas is 100,000 X smaller than atom

ROBERT MILIKAN 1909

ATOMIC THEORY

MASS/CHARGE OF ELECTRON

  • An experiment performed by Robert Millikan determined the size of the charge on an electron.
  • Put a charge on a drop of oil, measured how strong an electric field had to be to stop the drop from falling
  • He could calculate the force of gravity on one drop
  • He could then determine the electric charge that the drop must have

JAMES CHADWICK 1935

ATOMIC THEORY

PROTON NEUTRON MODEL

  • Chadwick reported the first accurate measurement of the mass of the neutron
  • finding it to be slightly greater than the mass of the proton
  • He then predicted that an unbound neutron is unstable and would undergo beta decay