-
460
Democritus
he died 370 B.C, he dun be an ancient greek flosifer -
Period: 460 to
atomic theory
-
johann becker and george stahl
Johann Becher (1635-1682) and Georg Stahl (1660-1734) developed the Phlogiston theory which dominated chemistry between 1670 and 1790. Basically, when something burned, it lost phlogiston to the air (after all, you could see the phlogiston leaving) A problem with the theory was that burning of metals resulted in an increase in the mass. This problem was solved by assigning negative mass to phlogiston. -
joseph priestly
Joseph Priestly (1733-1804) discovered oxygen (which he called "dephlogisticated air") in 1774. Priestly was an ardent phlogistonist until his dying day. Priestly was also an early anti-war activist who favored both the American and French Revolutions. He was shipped to the U.S. in 1791 where he lived a quiet life in Pennsylvania. His house was used as a starting point for the American Chemical Society in 1876. The Priestly Medal is the highest award given by to an American chemist by the S -
antonio lavoisier
Antoine Lavoisier (1743-1794) was the first person to make good use of the balance. He was an excellent experimenter. After a visit with Priestly in 1774, he began careful study of the burning process. 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. To support his work, Lavoisier was associated with a tax-collecting firm and was married to the -
joseph proust
Joseph Proust (1754-1826) proposed the the Law of Constant Composition in 1799. This law was very radical at the time and was hotly contested by Claude Berthollet (1748-1822). -
Dalton
he died in 1844 he proposed the atomic theory in 1803 -
amedeo avogadra
proposed what is now known as Avogadro's Hypothesis in 1811. The hypothesis states that at the same temperature and pressure, equal volumes of gases contain the same number of molecules or atoms. When this is combined with Gay-Lussac's Law of Combining Volumes, the only possible formulas for hydrogen, oxygen and water are H2, O2 and H2O, respectively. The solution to the atomic weight problem was at hand in 1811. However, Avogadro's Hypothesis was a radical statement at the time and was not -
joseph gay lussac
announced the Law of Combining Volumes in 1808. 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). -
Stanislao Cannizzaro
in 1860 at the Karlsruhe Conference, proposed that Avogadro's Hypothesis be accepted and the implications used for a period of five years. At the end of this five year period, a new conference would be called to discuss any problems that might develop; this second conference was never called. -
dimitri mendeleev
Dimitri Mendeleev (1834-1907) proposed the periodic law and developed the first periodic table in 1869. Medeleev's table was arranged according to increasing atomic weight and left holes for elements that were yet to be discovered. -
thomson
he thought of the cathode ray -
Nikola Tesla
he was the one who invented the tesla coil and he was and engineier -
millikan
determined the unit charge of the electron in 1909 with his oil drop experiment at the University of Chicago -
ruthiford
proposed the nuclear atom as the result of the gold-foil experiment in 1911 -
francis aston
Francis Aston (1877-1945) invented the mass spectrograph in 1920. He was the first person to observe isotopes. For example he observed that there were three different kinds of hydrogen atoms. While most of the atoms had a mass number of 1 he also observed hydrogen atoms with mass numbers of 2 and 3. Modern atomic masses are based on mass spectral analysis. His work led Rutherford to predict the existence of the neutron. -
Niels Bohr
he drew a picture of a atom with an tucleous and an proton -
henry moseley
Henry Moseley (1887-1915) discovered that the energy of x-rays emitted by the elements increased in a linear fashion with each successive element in the periodic table. In 1913, he proposed that the relationship was a function of the positive charge on the nucleus. This rearranged the periodic table by using the atomic number instead of atomic mass to represent the progression of the elements. This new table left additional holes for elements that would soon be discovered. Unfortunately, Mos -
james chadwick
James Chadwick (1891-1974) discovered the neutron in 1932. Chadwick was a collaborator of Rutherford's. Interestingly, the discovery of the neutron led directly to the discovery of fission and ultimately to the atomic bomb. -
Aristotle
he also dun be a greek falosifer and he died at 322B.C.
