Who am I?

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Who am I?
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Democritus

• He said you cannot cut a piece of matter
  infinitely, but at some point you would get the
  smallest piece of matter possible.
• All matter is composed of tiny, indivisible
  particles called atomos.
• 450 BC
• Greek Philosopher

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Antoine Lavoisier

• France 1872 (1879)
• Law of conservation of matter.
• Measured the mass of substances before and after
  a reaction and found that the masses were always
  equal. No mass was gained or lost in the
  reaction.
• Matter is conserved.

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John Dalton

• 1803-School teacher
• Studied the ratios in which elements combine in
  chemical reactions
• Formulated first Atomic theory of matter
• Each element is composed of extremely small
  particles called atoms.
• All atoms of a given element are identical, but
  they differ from those of any other element
• Atoms are neither created nor destroyed in any
  chemical reaction.
• A given compound always has the same composition
  or ratio of each atom

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JJ Thomson

• England 1897
• He discovered the electron while experimenting
  with cathode rays.
• He determined that the cathode ray was made of
  negatively charged particles electrons.
• He also was able to estimate that the mass of the
  electron was equal to about 1/1800 of the mass of
  a hydrogen atom.
• His discovery of the electron won the Nobel Prize
  in 1906.
• He showed that the production of the cathode ray
  was not dependent on the type of gas in the tube,
  or the type of metal used for the electrodes. He
  concluded that these particles were part of every
  atom.
• He created the plum pudding model of the atom.

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Ernest Rutherford

• Born in New Zealand 1871-1937
• Tested Thomsons theory of atomic structure with
  the gold foil experiment in 1910.
• Bombarded thin gold foil with a beam of alpha
  particles.
• If the positive charge was evenly spread out, the
  beam should have easily passed through.
• All of the positive charge and most of the mass
  of an atom are concentrated in a small core,
  called the nucleus.
• Gold Foil Experiment (alpha scattering)
• he determined that an atoms positive charge and
  most of its mass was concentrated in the core
  (most of the atom is empty space)
• he named the core the nucleus

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James Chadwick

• Neutrons- Discovered in 1932 (England 1891-1974).
  
• He bombarded Beryllium with alpha particles.
• Neutrons were emitted and in turn ejected protons
  from paraffin.

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Robert Millikan

• measured the charge of an electron using the oil
  drop experiment.
• x-rays gave the oil a negative electron
• 1.60x10-19 coulomb is the charge of an electron
• using Thomsons charge to mass ratio, he
  determined the mass of the electron is
  9.11x10-28g

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Cathode Ray Tube Experiment

• Performed by JJ Thomson
• Showed the existence of the electron.
• The ray is negative and composed of electrons.
• The negative end of a magnet attracts the beam.

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Gold Foil Experiment

• Performed by Ernest Rutherford
• Positive alpha particles were shot at a thin
  sheet of gold foil
• The deflection of the beam indicated the
  existence of a small, positively charged nucleus.

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Oil Drop Experiment

• Performed by Robert Millikan
• Determined the charge of the electron.
• 1909

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Thomsons Model of the Atom

• Called the plum pudding model
• The atom was comprised of positively charged
  matter with negative electrons stuck in the
  positive pudding

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Rutherfords Model of the Atom

• Contained a positive nucleus
• Electrons were around the outside of the nucleus

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Bohr Model of the Atom

• Nucleus in center with protons and neutrons
• Electrons are orbiting the nucleus in a set
  pattern
• Each orbital has a unique amount of energy

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Quantum Model of the Atom

• Contains a nucleus with protons and neutrons
• Electrons move very quickly around the nucleus,
  not in a circle or orbit, but randomly within an
  electron cloud.