ATOMIC THEORIES TIMELINE

Democritus
Born 460-370 B.C.
Discovered Atomic Theory

ATOMIC THEORY

• The first Atomic theory
• Found that all matter is made up of Atoms
• Atoms have an infinite number of atoms, size and shape

ARISTOTLE

• Born 384-322 B.C.
• Believed Earth, Fire, Wind and water made up all the elements
• Did not believe in the Atomic Theory
• Aristotle was later proved "wrong"
• He believed there was a fifth element called aether

John Dalton
Discovered experiment in 1803
The billiard ball

BILLIARD BALL

• Billiard ball experiment
• All matter is made up of atoms
• Found that Atoms are rearranged during a chemical reaction
• Discovered all atoms of the same element are the same
• Discovered this in 1803

JJ Thompson
Cadothe Ray experiment
Found in 1897

PLUM PUDDING

• Thompson believed hydrogen atoms had to be made up of 2000 electrons
• He discovered a negativley charged particle is bigger than a Hydrogen Atom
• Atoms balanced both negative and positive particles within them
• Found the charge to mass ratio of an electron

Rutherford
Gold Foil Experiment
1911

NUCLEUS DISCOVERY

• Rutherford didnt believe the electrons would bounce back
• 1 in 20,000 electrons came back from the foil
• This means that there is a different sized Nucleus in each atom

Milikan
Oil Drop Experiment
1913

ELECTRONS CHARGE SIZE

• Milikan discovered the size of the charge of an electron
• This was a great discovery of the electron
• He won a nobel prize in 1937
• Used JJ Thompson charge to mass ratio
• Found the exact mass and size of an electron

Chadwick
Alpha Source experiment
1932

NEUTRON DISCOVERY

• When he did the experiement he assumed electrons would be produced
• After pushing light through Beryllium and Parqffin Wax he found the Neutron
• He realized that the neutron must be an atom with no charge at all
• Also found that each Atom has a different atomic number