July 10, 2020
For educational institutions
Alyssa George, Riley Gloeckl, Grace Bair, Sonja Hebestreit
⟶ Updated 27 Sep 2017 ⟶
List of edits
Aristotle (322 BC) - no matter how many times you cut the same matter in half you would still have the same matter just smaller pieces
Democritus (400 BC) - ancient Greek philosopher, central figure in the development of the atom and of the atomic theory of the universe
Enrico Fermi (1942)
Murray Gell-Mann (1964)
Glen Seaborg (1951)
Glen Seaborg (1941)
Lise Meitner, Hahn, Strassman (1938)
James Chadwick (1932)
Paul Dirac (1932)
Robert Boyle (1688) - Boyle’s law, describes the relationship between absolute pressure and volume of gas
Johann Becher and George Stahl (dominated during the 1670s through 1790s) - the Phlogistic theory- when you burned something it lost phlogiston in the air. A problem of the theory resulted in different masses when metals were burned. The problem was fixed by assigning negative masses to phlogistons.
Antoine Lavoisier (1742) - He proposed the Combustion Theory which was based on sound mass measurements
Joseph Priestley (1774)- discovered oxygen
LaVoisier (1788) - Law of Conservation of Mass: matter can not be created or destroyed.
Proust (1794) - Law of Definite Proportions: a pure substance will always contain the same elements, combined in the same proportion for mass.
Joseph Gay-Lussac (1808) - announced the Law of Combining Volumes... He showed that at the same temperature and pressure, two volumes of hydrogen gas reacted with one volume of oxygen gas to produce two volumes of water (as a gas).
John Dalton (1830) -proposed an “atomic theory” with spherical solid atoms based upon measurable properties of mass
Amedeo Avogadro (1811) - equal volumes of gases, under the same conditions, have different masses
Michael Faraday (1832)- studied effect of electricity on solutions: 1) Electrolysis - the splitting of molecules with electricity 2) Developed law of electrolysis
J. Plucker (1859) - built one of the first gas discharge tubes (“cathode ray tube”)
Dmitri Mendeleev (1869) - put the elements into 7 groups with similar properties and discovered the Periodic Law
James Clerk Maxwell (1873) - published physical and mathematical theories of the electromagnetic field
Sir William Crookes (1879) - discovered cathode rays have properties of: traveling in a straight line from the cathode, cause glass to fluoresce, impart a negative charge they touch, are deflected by electric fields and magnets to suggest a negative charge, cause pinwheels in their path to spin indicating the have mass.
E. Goldstein (1886) - Used CRT to study “canal rays” which had electrical and magnetic properties opposite of an electron.
G.J. Stoney (1894)- proposed that electricity was made from electrons
Wilhelm Roentgen (1895) - rays that are coming from the CRT not deflected by a magnetic field called “X Rays”
Henri Becquerel (1896) - While studying the effects of x rays on photographic film, he discovered some chemicals spontaneously decompose and give off very penetrating rays.
J.J. Thomson (1897)- use a CRT to calculate the charge to the mass ratio of an electron = 1.759 x 10 8 coulombs/grams
J.J. Thomson (1897)- observed canal rays and realized the are connected to the proton H+
Rutherford (1898)- studied radiations emitted from uranium and thorium, he named this alpha and beta
Marie Curie (1898)- studied uranium and thorium, called their spontaneous decaying process “radioactivity”, discovered the radioactive elements polonium and radium with her husband
Soddy (1900)- observed spontaneous disintegration of radioactive element into variants he called “isotopes” or totally new elements, he discovered “half-life”, and made initial calculations on the amount of energy that is released during decay
Max Planck (1900)- used the idea of a quanta to explain hot glowing matter
Hantaro Nagaska (1903) - postulated a “saturnian” model of an atom with flat rings revolving around a positively charged particle
Abegg (1904) - discovered that inert gases had a stable electron configuration which led to their chemical inactivity
Philipp Lenard (1904) - He described atoms as mainly empty space filled with fast moving neutral particles, he called dynamites, were made of a heavier positive particle joined with a negative electron
Albert Einstein (1905) - published famous equation e=mc^2
Han Geiger (1906) - developed an electronic device to “click” when hit with alpha particles
R.A. Millikan(1909) - Oil drop experiment that determined the charge and mass of an electron
Ernest Rutherford (1911)- He used the alpha particles as atomic bullets, probed the atoms in pieces of thin gold foil. Established that the nucleus was very dense and very small and positively charged. He also assumed that the electrons were located outside of the nucleus
H.G.J. Moseley-(1914)- used and x ray tube to determine the charges on most nuclei in most atoms, He wrote the atomic number of an atom is the number of protons the have in the nucleus, this work was used to recognize the periodic table is based on the atomic number not the atomic mass.
Aston (1919)- discovered the existence of isotopes through the use of spectrograph
Niels Bohr(1922) - developed an explanation and model of an atomic structure and underlies regularities of the periodic table of elements
De Broglie (1923)- discovered electrons had a dual nature similar to both waves and particles.
Heisenberg (1927) - described atoms in a formula connected to the frequencies of spectral lines, proposed Principle of Indeterminacy- you can not know both the position of a particle or the velocity of the same particle
Cockcroft/ Walton (1929) - built an early linear accelerator and bombarded lithium with protons to produce alpha particles
Some event happened
The Manhattan Project
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