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400 BCE
Democritus
A Greek philosopher who proposed atoms were the smallest unit of matter -
John Dalton
Theorizes all elements are:
-Composed of atoms
-Atoms of the same element are identical
-Atoms combine in various combinations of whole number ratios to make all known forms of matter -
J.J. Thomson
Discovers electrons via the cathode-ray tube experiment and theorizes all electrons are dispersed in atom randomly (hence the plum-pudding model). -
Cathode-Ray Tube Experiment
An experiment conducted by J.J. Thomson. It proved the existence of electrons by showing the particles in a electric beam in a cathode ray tube were negative as they were attracted to positively charged objects -
Eugen Goldstein
Eugen Goldstein was a German physicist who is credited with finding the proton -
Ernest Rutherford
An New Zealander who discovered (via the Gold Foil Experiment) that Electrons are found outside the nucleus. -
Gold Foil Experiment
An experiment by Rutherford aimed at beam of alpha particles at a sheet of gold foil which was surrounded by a screen that fluoresced when electron from the alpha particles hit it. Rutherford expected them to pass right through the foil due to the plum pudding model stating electrons were situated in the nucleus. Instead they bounce of at varying angles due to the mass being centered in the nucleus and bouncing off the nuclei of the gold atoms (a fact confirmed by the experiment). -
Niels Bohr
A danish physicist who won the Nobel Prize for his Theory of Electron Orbits which states electrons revolve in set orbits around the nucleus. -
Louis de Broglie
A French physicist who won a Nobel Prize for propsing electrons do not travel in set orbits but instead move like waves. -
Erwin Schrodinger
Erwin Schrodinger was a Nobel prize winning Austrian physicist who calculated the movement of electrons mathematically. His calculations are the basis of electron cloud theory which staes that electrons move randomly in clouds in which there is a certain probability of finding an electron at any given point. The theory holds the denser the cloud is at any particular spot the higher the probability an electron will be there. -
James Chadwick
A English physicist who discovered neutrons
