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465 BCE
Democritus (460BC-370BC)
Democritus was an Ancient Greek philosopher. He was the first person to suggest the existence of atoms. Based on philosophy, he believed that atoms were invisible and indestructible. -
Antoine Lavoisier (1743-1794)
Antoine-Laurent de Lavoisier was a French nobleman and chemist. He created the Law of Conservation of mass which states that matter can not be made or destroyed. The total mass of products is the same as the sum of the masses of the reactants.
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John Dalton (1766-1844)
John Dalton was an English chemist, physicist, and meteorologist. He discovered that all elements are composed of atoms and atoms of the same element are identical. Atoms of different elements combine in simple whole number ratios to form chemical compounds. In chemical reactions, atoms are combined, separated or rearranged, but don't change into atoms of another element.
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Dmitri Mendeleev (1834-1907)
dimitri mendeleev was very passionate about chemistry but always wanted to find a way to organize it. He found a way to organize it using the atomic mass. The organization table he discovered is known as the periodic table of elements all sorted from least to greatest atomic mass.
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Eugen Goldstein (1850-1930)
Eugen Goldstein was the first to discover the existence of the proton in 1886. He observed the proton is a positive charged subatomic particle and has a relative mass of 1. He also brought to the attention of the canal rays that ate positively charged and run the opposite direction of the the other rays.
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Max Planck (1858-1947)
Max Planck is most famous for his discovery of the atomic theory. This theory describes the behavior of the energy and mass at an atomic and subatomic level.
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Ernst Rutherford (1871-1937)
Ernest Rutherford began his studies on the atom in 1917 where he then was the first to split the atom and determine the nucleus. His conclusions from his gold foil experiment are that the nucleus is small, dense, and positively charged.
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Erwin Schrodinger (1887-1961)
Erwin Schrodinger is most famous for his spin on the Bohr atomic theory where instead of predicting the odds of where an electron could end up he found a way to predict the exact path in which the electron would follow to reach its next destination.
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Henry Moseley (1887-1915)
Henry Moseley was an English physicist who help contribute to the study of the atom by using x-ray spectra to more closely examine the atom. The application resulted in the now accurate positioning of all the elements in the periodic table.
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Werner Heisenberg (1901-1976)
Werner Heisenberg is most famous for his contribution of quantum mechanics to the atomic theory. Werner would use mathematical equations to back up his predictions of the behavior of electrons and subatomic particles in the atom.
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J.J. Thomson (1856-1940)
Joseph John Thomson was an English physicist. He discovered the negatively charged particles in atoms, which are electrons. The "Plum Pudding" model describes how electrons, like plums, are embedded in positively charged "pudding".
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Robert Millikan (1868-1953)
Robert Millikan was an American experimental physicist. He determined the mass of an electron using his oil drop experiment. The mass of an electron is 1/1,840.
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Niels Bohr (1885-1962)
Niels Bohr was a Danish physicist. He founded the Bohr Atomic Model which states that electrons move in orbits of fixed size and energy.
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James Chadwick (1891-1974)
James Chadwick was an English physicist. He discovered the neutron, which is found in the nucleus with protons. Neutrons have the same mass as a proton and have no charge.
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