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430 BCE
Plague of Athens
A plague struck Athens during the Peloponnesian War, the great struggle between Sparta and Athens. -
430 BCE
Democritus: discovery of the atom
460 BCE - 370 BCE
Democritus was the first person to create a model of the atom. He believed that all human bodies were made up of particles so small they were invisible, and atoms were solid particles moving around randomly in empty space. Democritus set up the model of the atom as being a solid ball. -
Second Symphony
Beethoven performed the Second Symphony for the first time. This was the second symphony that he wrote. -
John Dalton: created more specific properties of the atom
September 6th, 1766 - July 27th, 1844
John Dalton created the atomic theory. This did not change the atom's model, but it did add more properties to the atom. These include the fact that atoms of the same element are identical in size and mass and combine to create simple whole-number ratios. Also, atoms cannot be created, destroyed, or divided, and finally, in chemical reactions, atoms are combined, separated, or rearranged. (Some of these properties are not correct.) -
Michael Faraday: learnt that atoms possess an electrical component
September 22nd, 1791 - August 25th, 1867
Through experiments concerning electricity, Michael Faraday discovered that atoms have an electrical component. By running an electrical current through multiple substances Michael observed that the individual component’s atoms separated. This proved that atoms had an easily manipulated electric component. This changed that atomic model because now atoms had particles with an electrical charge or in other words, electrons. -
Eugen Goldstein: created the idea of the proton
September 5th, 1850 - December 25th 1930
Eugen Goldstein added to the atomic model with his discovery of the proton. He discovered the proton through his canal ray experiment. Cathode rays, or electrons, travel in the opposite direction of canal rays, protons. So Eugen concluded that they must be opposite charges. -
Tragic Death
The painter Vincent Van Gogh died in France due to a suicide attempt two days earlier. -
JJ Thomson: proved the existence of smaller particles
December 18th, 1856 - August 30th, 1940
JJ Thomson proved the existence of smaller particles within the atom. He found that the particles that made up cathode rays, which are electrical currents, were smaller than atoms. This made him come to the conclusion that there are smaller particles within the atom. Finally, the model of the atom is changed from simply a sphere to a sphere containing electrons and protons inside. -
Robert Millikan: discovered specific information concerning the electron
March 22nd, 1868 - December 19th, 1953
In 1910 Millikan learned many more exact details about the electron. Millikan learned the exact size was 1/1837 compared to a hydrogen atom. He also learned the exact charge of an electron. This allowed more models of the atom to be exact and have more specific information. -
Ernest Rutherford: learnt that the atom was mostly empty space
August 30th, 1871 - October 19th 1937
Ernest was the first to discover that the atom was mostly made up of empty space. He found that all of the atom's mass was in the center so it could not be a complete solid. So the atomic model was once again changed from a solid ball containing electrons and protons to a nucleus of protons surrounded by empty space and electrons. -
Titanic
The Titanic struck its iceberg and sank. This killed over 1,500 people. -
Niels Bohr: discovered how electrons move in orbital motions
October 7th, 1885 - November 18th, 1962
In three articles Niels Bohr explained his new and improved model of the atom, now called the Bohr model. The model depicts a nucleus of protons being circled by various orbits of electrons. Niels believed that electrons had to move in a certain orbit because of their specific energy amount. This changed the model from electrons moving randomly to them having particular movements. -
19th Amendment
The 19th Amendment was passed in the US which made it illegal to deny someone the ability to vote based on sex. This allowed women to finally vote. -
Werner Heisenberg: created the uncertainty principle which is necessary for understanding the electron
December 5th, 1901 - February 1st, 1976
Werner contributed to the atomic theory and model by coming up with the uncertainty principle. The principle states that it is not possible to know the momentum or exact position of a particle at the same time. So we cannot know exactly where and how fast an electron is. This enforces the “electron cloud” model because we cannot know the specific behaviors of an electron and instead can use the cloud to represent where an electron would most likely be. -
Erwin Schrodinger: discovered that electrons move in a wave-like matter
August 12th, 1887 - January 4th, 1961
Erwin came up with a hypothesis that electrons move as if they are waves or in other words, electrons follow wave-like-duality. His observations of the atom led him to realize that electrons move in standing waves. This led to Erwin's creation of the “electron cloud model”. The model does not give electrons specific movements but depicts them as always moving. -
Stock Market Crash
A large stock market crash took place in 1929. This set off a reaction leading to the Great Depression. -
James Chadwick: discovered neutrons
October 20th, 1891 - July 24th, 1974
James Chadwick was the first to discover neutrons within the nucleus. This contribution completed the model that we have today. There was already speculation of more particles in the nucleus due to isotopes but James proved it by his experiment with beryllium. He bombarded beryllium with alpha particles which produced a radiation made up of particles equal in mass to protons. This led to the conclusion of neutrons and the final change of the atomic model.