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Period: 322 to
Aristotle
He believed that the universe was eternal and that objects had potential (matter) and reality (form). -
Period: 346 to
Plato
Founded the Academy, which trained many philosophers, and gave each of Empedocles' elements a shape; fire was a tetrahedron, air was a octahedron, water was a icosahedron, and earth was a cube. He also thought all the properties could be discovered through thought, not experimentation. -
Period: 370 to 460
Democritus
Said that atoms were solid with infinite sizes, shapes, and number, but were always too small to see. Also thought that everything emitted atoms and this is how our senses work. -
Period: 420 to
Leucippus
Thought there was two elements, solid and empty. He also believed that atoms existed and determined the properties of matter. He also thought that without space there is no motion -
Period: 430 to
Empedocles
Believed there were 4 elements; Earth, Fire, Water, and Air. Showed air took up space and believed that light had a speed. -
Oct 5, 1086
Fall of Greece
Greece was taken by the Romans in 86 B.C., after the Romans sacked Athens. The Greek teachings and scholars were favored by the Romans, and many Greeks thought in Rome, while many Romans went to Greece to learn at places like the Academy. -
Period: to
John Dalton
Created three laws for matter and published them in 1803:
1. If two elements can combine into multiple compounds, the ratios between the two elements would be whole numbers.- When elements combine into compounds, they maintain a ratio no matter the amount of the compound.
- Matter cannot be destroyed, and in a closed circuit there is no loss in mass after a reaction.
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Period: to
Joseph James Thomson
Published several books in atomic structure during the 1880s and in 1904, suggested his model of the atom. His model is a sphere of positive matter with electrons throughout, with total charges that cancel to create a neutral atom. It is called the Raisin Bread theory. -
Period: to
Max Plank
E=h*f, where h is his constant of 6.63*10^-34 j/s. The energy depends of the frequency, so the right frequency causes an atom to absorb energy and jump up a level. When the electron goes back to its ground state, it emits a photon of light. -
Period: to
Hantaro Nagaoka
He proved that electrons do not lose energy when they go around the nucleaus of the atom. He based his model off Saturn's rings, so it is called the saturnian atomic model. Bhor's model is very similar to Nagaoka's, but with more detail. -
Period: to
Robert Millikan
He created the oil drop experiment and discovered the charge of electrons with it. -
Period: to
Ernest Rutherford
He claimed that all elements have half-lives, and that over time radioactive isotopes become stable. He also discovered two types of radiation, alpha and beta rays. In 1909 he discovered the nucleus of the atom. -
Period: to
Neils Bhor
Using Rutherford’s model, Bhor decided that electrons orbit the nucleus in energy levels. His model is similar to Nagaoka's -
Period: to
Erwin Schrodinger
He invented the Quantum Mechanical Model, which predicts the location of electrons in the atom. It is composed of orbitals with complex shapes that get further away from the nucleus. His model replaced Bohr’s -
Period: to
James Chadwick
He discovered neutrons by bombarding beryllium with alpha particles. He then used the velocity of the partials emitted, called nuclear, using the mass. Beryllium was bombarded again, and the radiation captured in a wax. From the wax, Chadwick discovered neutrons. -
Period: to
Louis de Broglie
Broglie devolved wave-particle duality, which says that particles behave like particles and waves at the same time, being both and neither. This idea gave birth to quantum physics. -
Period: to
Werner Heisenberg
Heisenberg decided that when a person measures one aspect of a subatomic particle, they alter the others. This means that all measurements cannot be relied on, and you never know the state of the particle. -
World War 1 begins
The Germans helped the Austro-Hungarian Empire put down an insurrection, causing the Russians to fight them to protect the rebels, and drawing France and England into the conflict. The U.S. joined the conflict after several attacks on the merchant fleet. -
World War I ends
After the U.S. joined the conflict, the Germans surrendered and the peace was decided at Versailles. -
World War 2 begins
WWII began when Hitler, the leader of Nazi Germany, invaded Poland, France, England, Soviet Russia when Hitler invaded them, and the U.S. when the Japanese attacked Pearl Harbor, Fought against the Germans, Italians, and Japanese. -
World War 2 ends
WWII ended when the Japanese surrendered to the U.S. after the U.S. dropped two atomic bombs on Hiroshima and Nagasaki. The war in Europe ended slightly earlier.