EVOLUTION OF THE ATOM

DEMOCRITUS - 400 BCE

ATOMOS THEORY

• Believed all matter contained atoms.
• Thought atoms were indestructible.
• Atoms were solid.
• Atoms differed in size and shpe.
• First person to come with the theory of atomos.

ARISTOTLE - 332 BCE

EARTH, WIND, WATER, AND FIRE

• Believed matter could be cut in half infinitely.
• Believed everything was made up of the four elements.
• Caused Democritus's theory to be overlooked for 2000 years.
• Aristotle's theory was wrong.

JOHN DALTON - 1803

BILLIARD BALL MODEL

• Was one solid shape.
• Uniform throughout.
• All atoms were indivisible and indestructable.
• During a chemical reaction atoms are rearranged.
• Compounds happened when two different atoms combined.

J.J. THOMSON - 1897

PLUM PUDDING MODEL

• Negetively charged electrons
• Surrounded by a positive sphere
• Discovered electron with cathode ray experiment.

RUTHERFORD - 1898

POS. CHARGED NUCLEUS MODEL

• Positively charged nucleus.
• Negatively charged electrons.
• Proposed the existence of the neutron
• ^^Using gold foil experiment.

MILIKON - 1908

MASS CHANGE ELECTRON

• Used oil drop experiment.
• Determined the mass of an electron.
• Also determined the charge.

CHADWICK - 1932

PROTON NEUTRON MODEL

• Most similar to our ideas today.
• Found the neutron.
• Electrons orbit around a positive nucleus.
• Nucleus made up of neutrons and protons.