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322
Aristotle
Aristotle
He believed in the four elements of air, earth, water and fire. Aristotle felt you would always have a smaller piece of matter if you keep cutting it in half. -
400
Democritus
He had a theory that stated that matter could not be devided into smaller pieces. They would eventually become the smalles they can become and invisible. He named the smallest pieces "atomos" which mean "not to be cut." -
Jan 13, 1144
Second Crusade
The Second Crusade is started by Bernard of Clairveaux after the Christian kingdom of Edessa falls to Muslims. -
Jan 13, 1149
Oxford University
Oxford University is founded in England. -
Jan 13, 1348
Black Plague
The Black Plague in Europe kills about 75 million people. -
Jan 13, 1517
Martin Luther
Martin Luther
An Augustinian monk, Martin Luther, nails his 95 theses to the church door in Wittenberg. He unknowingly initiated the Protestant revolution. -
Jamestown
The English settle in Jamestown. -
Treaty of Paris
The French and Indian War is ended with the Treaty of Paris. Britain gains all of North American east of the Mississippi, important parts of India, and various islands from the French. Many American colonists, most notably George Washington, gain military experience in the conflict. -
Antonie Lavosier
He proposed the Combustion Theory which was based on sound mass measurements. He named oxygen. He also proposed the Law of Conversation of Mass which represents the beginning of modern chemistry. -
Joseph Proust
He proposed the Law of Constant Composition. -
John Dalton
John DaltonDalton's theory stated that the atoms of different elements could be distinguisehd by differences in their weights. -
Amadeo Avagadro
His hypothesis says that at the same temperature and pressure, equal volumes of gases contain the same number of molecules or atoms. -
Origin of Species
Charles Darwin publishes Origin of Species. -
William Crookes
He studied the effects of sending an electric current through a gas in a sealed tube. The tube had electrodes at either end and a flow of electrically charged particles moved from one of electrodes. This electrode was called the cathode, and the particles were known as cathode rays . -
Henri Becquerel
While studying the effect of x-rays on photographic film, he discovered some chemicals spontaneously decompose and give off very penetrating rays. -
J.J. Thomson
Discovered the electron in a series of experiments designed to study the nature of electric discharge in a high-vacuum cathode-ray tube, he estimated the value of the charge itself. -
Madame Curie
CurieStudied uranium and thorium and called their spontaneous decay process "radioactivity". She and her husband Pierre also discovered the radioactive elements polonium and radium. -
Max Planck
He used the idea of quanta, (discrete unit of energy) to explain hot glowing matter -
Robert Millikan
Determined the unit charge of the electron with his oil drop experiment at the University of Chicago. This allowed the calculation of the mass of the electron and the positively charged atoms. -
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Earnest Rutherford
Established that the nucleus was very dense, very small and positively charged. He also assumed that electrons were located outside outside the nucleus. -
Henry Moseley
Using x-ray tubes, he determined the charges on the nuclei of most atoms. He wrote "The atomic number of an element is equal to the number of protons in the nucleus". This work was used to reorganize the periodic table based upon atomic number instead of atomic mass. -
Niels Bohr
Developed an explanation of atomic structure that underlies regularities of the periodic table of elements. His atomic model had atoms built up of successive orbital shells of electrons. -
Louis deBroglie
His theory states that particles can behave like waves, and waves (radiation) can behave like particles. -
Heisenberg
He described atoms a formula connected to the frequencies of spectral lines. Proposed Principle of Indeterminacy - you can not know both the position and velocity of a particle. -
Erwin Schrodinger
Viewed electrons as continuous clouds and introduced "wave mechanics" as a mathematical model of the atom. -
James Chadwick
Using alpha particles he discovered a neutral atomic particle with a mass close to a proton. Because of this the neutron was discoverd. -
World War II
Germany invaded Poland and started World War II. -
Neil Armstrong
Neil ArmstrongNeil Armstrong, an American, steps out of his lunar landing module to become the first human being to set foot on the moon. -
Nelson Mandela
Future South African President walks out of jail after 27 years in the custody of the white apartheid government.
