Chemistry history of Atoms

Democritus

was the first person to propose the existence of atoms 460 BC Theory~Everything is made up of ‘atoms’ ~ small, unbreakable spheres

John Dalton

1803 Very similar to Democritus

JJ Thompson

1898

Cathode ray experiment In the presence of a magnet

Ernest Rutherford

1909

Gold Foil Experiment Positive charged particles were shot at a piece of thin gold foil Most particles passed through the sheet, but some were deflected back

Neils Bohr

1913

Based on Rutherford’s work Bohr used mathematical calculations to determine the most likely locations of electrons He theorized that electrons are located in “orbits” around the nucleus called orbitals

James Chadwick

1932

The nucleus contains relatively large particles that contain no charge, known as neutrons

Schrodinger

1925

Electrons are not particles, but are actually more like waves The nucleus is surrounded by an “electron cloud” Electrons are more likely to be located in some areas than others

Heisenberg’s Uncertainty Principle

1930

Using his mathematical background Heisenberg determined it is IMPOSSIBLE to know both the exact speed and location of an electron at any given time Quantum Theory