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Antoine Lavoiser
Lavoiser contributed to the Atomic Theory, by defining the law of conservation of mass. Study.com states that "Antoine Lavoisier's work in defining the law of conservation of mass would help to shape atomic theory." This was important to the Atomic Theory because it showed that all matter was made up of atoms. These atoms were not destroyed or produced during a chemical reaction. -
Democritus/Dalton's Model
This development was first stated in 1803 by John Dalton. Dalton's theory states that "all matter was compromised of indivisible and indestructible atoms with distinct masses and properties." Elements have small indivisible atoms, and atoms of the same element are identical. The model was also introduced in 400 BCE by the Greek philosopher, Democritus. -
The Proton
Eugene Goldstein contributed to the ATomic theory also, he was the first to discover evidence of protons or "positively charged particles." BCS states that "Goldstein concluded that in addition to the electrons, or cathode rays, that travel from the negatively charged cathode toward the positively charged anode, there is another ray that travels in the opposite direction, from the anode toward the cathode." -
Antoine Henri Becquerel
Henri Becquerel contributed to the Atomic Theory by his discovery of radioactivity. The American Board states that "In 1896, Henri Becquerel was studying the fluorescent properties of uranium salts and placed a piece of the uranium salt on top of a photographic plate wrapped in black paper. He discovered, upon development, that the plate was exposed in the shape of the uranium sample. Becquerel had discovered radioactivity." -
Thomson's Model
The Thomson Model was discovered by J.J. Thomson in 1897. Khan Academy states that "all atoms contain tiny negatively charged subatomic particles or electrons." Thomson did lots of experiments with the cathode ray tubes, which helped lead to his discovery. Khan Academy states that "Thomson proposed the plum pudding model of the atom, which had negatively-charged electrons embedded within a positively-charged "soup." -
Quantum Mechanical Model
The Quantum Mechanical Model was discovered on December 14, 1900, by Max Planck and Niels Bohr. The quantum theory was discovered through various physical experiments. This model changed the understanding of the atom, because "It hinges on the idea that the universe is not as predictable as previously thought." -
Robert Millikan
Robert Millikan contributed to the Atomic Theory by his "accurate determination of the charge carried by an electron, using the elegant “falling-drop method.” This led to his demonstration of the atomic structure of electricity. -
Rutherford's Model
Rutherford's Model was discovered in 1911 by Ernest Rutherford. Chemistry LibreTexts, "In the nuclear atom, the protons and neutrons, which comprise nearly all of the mass of the atom, are located in the nucleus at the center of the atom." Rutherford's model became known as the nuclear model. The Rutherford model changed the understanding of the atom because "Rutherford established that the mass of the atom is concentrated in its nucleus." -
Bohr's Model
The Bohr's Model was discovered in July of 1913 by Niels Bohr. This model changed the understanding of the atom because Bohr suggested "electrons "jump" between energy levels (orbits) in a quantum fashion." The Bohr theory altered the atomic theory model by explaining that "electrons move in fixed orbitals (shells) and not anywhere in between." -
Period: to
Quantum Mechanics
Louis DeBrogile, Werner Heisenberg, and Erwin Schrödinger were a small group of physicists. They were the first to explore the theory of quantum mechanics. -
Subatomic Particle's Discovery
Sir James Chadwick discovered the neutron. It was found when Chadwick "fired radiation at beryllium sheet from a polonium source." The proton was discovered in 1917 by Ernest Rutherford. According to BYJU's.com, "his scintillation detectors detected hydrogen nuclei when a beam of alpha particles was shot into the air." The electron was discovered in October 1897 by Joseph. According to Khan Academy, it was found by "J.J. Thomson's experiments with cathode ray tubes."