-
150
Ptolemy
produced the genetic model of the solar system -
300
Aristotle (B.C.)
all matter was made up of fire, earth, air, and water. -
400
Democritus (B.C.)
He came up with the idea that everything could be broken down into smaller pieces (atoms). -
500
Leucippus (B.C.)
the earliest Greek to develop the theory of atomism — the idea that everything is composed entirely of various imperishable, indivisible elements called atoms. -
Oct 8, 1494
Luca Pacioli
first codification of the Double-entry bookkeeping system -
Oct 8, 1543
Andreas Vesalius
pioneering research into human anatomy -
Antoine Lavoisier
found elements that make up water and named them -
Joseph Priestley
discovered oxygen -
Joseph Proust
Law of Constant Composition. Developed the use of hydrogen sulfide as a reagent give results of his chemical analyses in terms of percentage weights. -
Joseph Gay-Lussac
Created the law of combining volumes -
John Dalton
Believed that the atom was the smallest unit of matter, and couldn't be broken down. He tried to calculate atomic weight of compounds and atomic structures of atoms. -
Stanislao Cannizzaro
He is remembered today largely for the Cannizzaro reaction and for his influential role in the atomic-weight deliberations of the Karlsruhe Congress. -
Amedeo Avogadro
Avogadro’s Hypothesis; states that at the same temperature and pressure, equal volumes of gases contain the same number of molecules or atoms. -
William Crookes
responsible for reconstructing the Cathode Ray, discovered the element thallium and show there is a negative charge in atoms. -
Dmitri Mendeleev
He formulated the Periodic Law, created his own version of the periodic table of elements -
Madame Curie
the strength of radiation didn’t depend on the compound that was being studied. It only depended on the amount of uranium or thorium. Came to the conclusion that the ability to radiate did not depend on the arrangement of the atoms in a molecule, it must be linked to the interior of the atom itself. -
J.J. Thomson
discovered electrons with a cathode-ray tube, and made the Plum Pudding Model. Used a CRT to experimentally determine the charge to mass ratio (e/m) of an electron =1.759 x 10 8 coulombs/gram. -
Henri Becquerel
Discovered uranium produced x-ray radiation--led discovery of radioactivity; showed atoms can’t change shape or are divisible. -
Max Planck
used the idea of quanta (discrete units of energy) to explain hot glowing matter. founded the Quantum Theory -
Robert Millikan
responsible for finding the charge of a single electron; proved that subatomic particles exist. -
Ernest Rutherford
discovered the nucleus, and created the Planetary System model -
Henry Moseley
Found the relationship between wavelengths, what x-rays produced, and atomic number of a metal; known as Mosely's Law. -
Niels Bohr
Created a new model that allowed electrons to be outside the nucleus and orbit around the nucleus. -
Francis William Aston
invented the mass spectrograph; Discovered a large amount of isotopes--three different kinds of hydrogen atoms. -
Louis de Broglie
Discovered that electrons had a dual nature-similar to both particles and waves. -
Werner Heisenberg
came up with the uncertainty principle. Described atoms by means of formula connected to the frequencies of spectral lines -
Erwin Schrödinger
Viewed electrons as continuous clouds and introduced "wave mechanics" as a mathematical model of the atom. Came up with the equation for quantum wave mechanics--reason electrons move in an atom. -
James Chadwick
proved existence of neutrons. Using alpha particles discovered a neutral atomic particle with a mass close to a proton. Thus was discovered the neutron. -
Albert Einstein
mathematical method to calculate the size of atoms and molecules
