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400
The First Concept
Democritus came up with the Atomic Theory concept. -
Period: 400 to
Atomic Theories
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460
Democritus
Saw the world and everything in it as endless motion of small, indivisible particles- “atomos”. Named the atom as the building block of matter. -
Jan 1, 1492
Columbus
Columbus discoverd land in the new world which is now the Bahamas. -
Sep 16, 1565
First Settlement
The first settlement of North America takes place in St. Augustine, Florida -
Printing Press
The first printing press in America arrives. -
Antoine Lavoisier
Lavoisier first outlined the Principle of Conservation of Mass. Said that one element could not change into another. Lavoisier’s concept of an element provided the foundation for Dalton’s atomism. -
American Philosophical Society
The American Philosophical Society is founded in Philadelphia by Ben Franklin -
Electricity
Ben Franklin discovers electricity. -
Joseph Louis Proust
Proust proposed the law of constant composition, which states that the ratio by mass of the elements in a chemical compound is always the same, regardless of the source of the compound. Helps in the development of universal laws. -
Independence
Declaration of Independence is signed by members of Congress. -
George W.
Washington is elected to be president. -
Law of Conservation of Mass
Says mass is an isolated system and will remain constant and that matter can neither be created nor destroyed. Lavoisier's concept of an element provided the foundation for Dalton's atomic theory. -
Law of Definite Proportions
States that a given chemical compound always contains the same proportion by mass of its constituent elements. Discovered by Proust. Helps in the development of universal laws. -
John Dalton
Proposed an "atomic theory" with spherical solid atoms based upon measurable properties of mass -
Dalton's Atomic Theory
States that elements consist of tiny particles called atoms. All atoms of an element are the same and have the same mass. Provided further reason to believe that atoms are the building block of matter by providing the weight of careful chemical measurements. -
Ice Cream is created
Augustus Jackson, an African American confectioner, created multiple ice cream recipes, and he invented a superior technique to manufacture ice cream. -
California Gold Rush
Gold is discovered in California. People form all overe the contry flood into California, followed by people form all over the world. It brought many people to America looking for money, and started the settelement of the west. -
Dmitri Mendeleev
Arranged elements into 7 groups with similar properties. He discovered that the properties of elements "were periodic functions of the their atomic weights". This became known as the Periodic Law. -
The Telephone
Alexander Graham Bell sucessfully tests the telephone with his assistant. It revolutionizes communication due to it ease of use and more efficient to use than the telegram or previous methods of communication. -
Light Bulb
Thomas Edison officially creates the first pratical electrically powered light bulb. This changed the world because it now allows for industrial processes to continue into the night due to the greater amount of light output compared to a candle. Workers can now work anytime of day. -
J.J. Thompson
Studied "canal rays" and found they were associated with the proton H + . -
Cathode Ray Tube
Tubes with all the air sucked out of them would give off a florescent light when high voltage was pumped into them. Led to the discovery of the electron by J.J Thompson -
Quantum Theory/ Max Planck
Max Planck Theory states that the energy of each quantum is equal to the frequency of the radiation multiplied by the universal constant: E=f*h, where h is 6.63 * 10E-34 Js. -
First Powered Flight
The first time in hstory that a machine is made that powers itself for flying. Orville and Wilbur Wright successfully started a major revolution in flying technologhy that was to affect the way we move. -
Albert Einstein
Devised a mathematical method of calculating
the size of atoms and molecules. -
Gold Foil Experiment
Rutherford fired Alpha particles at a sheet of gold foil. He found that most passes through the foil but some bounced off. Proved Thomson’s raison bread experiment wrong and helped discover the nucleus. -
Robert Millikan
Oil drop experiment determined the charge (e=1.602 x 10 -19 coulomb) and the mass (m = 9.11 x 10 -28 gram) of an electron. -
Ernest Rutherford
Using alpha particles as atomic bullets, probed the atoms in a piece of thin (0.00006 cm) gold foil . He established that the nucleus was: very dense,very small and positively charged. He also assumed that the electrons were located outside the nucleus. -
Hemry Mosely
Using x-ray tubes, 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 sucessive orbital shells of electrons. -
Erwin Schrodinger
Viewed electrons as continuous clouds and introduced "wave mechanics" as a mathematical model of the atom. -
James Chadwick
Using alpha particles discovered a neutral atomic particle with a mass close to a proton. Thus was discovered the neutron. -
Lise Meitner
Conducted experiments verifying that heavy elements capture neutrons and form unstable products which undergo fission. This process ejects more neutrons continuing the fission chain reaction. -
Terrorist Attack
Terrorist Hijack 4 planes in the U.S.Two Planes crash into the Twin Towers. One Crashed into the Pentagon and the other crashed into a empty field in Pinnslyvania.. -
Ernest Rutherford
Studied radiations emitted from uranium and thorium and named them alpha and beta. -
Marie Curie
Studied uranium and thorium and called their spontaneous decay process "radioactivity". She and her husband Pierre also discovered the radioactive elements polonium and radium. -
Eugene Goldstein
Used a CRT to study "canal rays" which had electrical and magnetic properties opposite of an electron.