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400 BCE
Democritus
460-370 B.C
He conceived the idea that matter was made up of particles which he called atoms. A name derived from the Greek word atomos. -
350 BCE
Aristotle
381-322 B.C.
He believed in the 4 elements of air, earth, water, and fire. Felt that regardless of the number of times you cut a form of matter in half, you always have a smaller piece of that matter -
Antoine Lavoisier
1743-1794
Established the law of conservation of matter. -
John Dalton
Contribution to the Atomic Theory occurred in 1803
Established Daltons Theory:
*Matter is composed of extremely small particles called atoms
*Atoms are invisible and indestructible
*Atoms of specific are different than those of a different elements
*In a chemical reaction, atoms separate, Combine and/or rearrange. -
J.J. Thomson
Thomson created the Cathode Ray, the Cathode Ray is a tube that when a high voltage of electricity is sent through it the atoms hit the outside of the tube to make it glow. -
Robert Millikan
Robert Millikan measured the charge of a single electron. This is known as the elementary charge, one of the fundamental physical constants. -
Ernest Rutherford
Ernest Rutherford known as the father of nuclear physics, developed the theory for the structure of the atom. He used a gold foil experiment, observing the scattering of alpha particles, and demonstrated for the first time the existence of the atomic nucleus. -
Niels Bohr
Neils Bohr developed the Bohr atomic model, with electrons travelling in orbits around the nucleus, and chemical properties being determined by how many electrons are in the outer orbits. He also integrated the Planck quantum theory, stating that when electrons change orbits they emit a quantum of discrete energy. -
Erwin Schrodinger
Erwin Shrodinger described how electrons move in wave form, and developed the Schrodinger equation which describes how the quantum state of a system changes with time. -
James Chadwick
James Chadwick discovers the neutron component of the atomic nucleus, explaining the nuclear fission of uranium 235. This also made it possible to produce elements heavier than uranium in the lab. -
Werner Heisenburg
One of his most memorable discoveries is the Uncertainty Principle. He said this means that electrons do NOT travel in neat orbits. Also, all electrons that contain photons will then change momentum and physics. -
Murray Gell-Mann
He showed scientists what makes up protons and neutrons, quarks. Protons contain two up quarks and one down quark, while neutrons contain two down quarks and one up quark. This makes neutrons have its negative charge, because it has more down quarks than up quarks. Making up all visible matter, the knowledge of the quark will help future scientists in their studies.
