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400
Democritus (Circa 400 B.C.)
Democritus said that all matter is made up of tiny, indivisible particles called atoms. These atoms were completely solid and were eternally in motion. He said every matter is made of same atoms. He also stated that every different type of atom differs slightly. -
400
Democritus Atom Model
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Period: 400 to
Atomic Models Timeline
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Antoine Lavoisier
Antoine-Laurent de Lavoisier was a French nobleman and chemist central to the 18th-century Chemical Revolution and a large influence on both the histories of chemistry and biology. He is widely considered to be the "Father of Modern Chemistry’’. -
Lavoisier's Atom Model
Antoine Lavoisier formulated the theory of conservation of mass. This showed that matter (atoms) couldn’t be created or destroyed, which supported the theory of Democritus. Lavoisier also showed that compounds are simply combinations of different types of atoms, further supporting the idea that atoms are indivisible. -
John Dalton
Dalton compounded all the work of Lavoisier and Democritus into one, single atomic theory. This theory stated that all matter is made of indivisible and indestructible atoms, all atoms of a given element are identical, compounds are combinations of elements (atoms), and a chemical reaction is merely a rearrangement of atoms. -
Marcel Proust (1754-1826)
Joseph Proust's contribution to the atomic theory was that he research and declared that a substance has the same composition where ever or how ever it was made. He discovered that the same substance found in different areas of the world had the same elements at the same ratio. -
Faraday (1791-1867)
Studied the effect of electricity on solutions, coined term "electrolysis" as a splitting of molecules with electricity, developed laws of electrolysis. Faraday himself was not a proponent of atomism. -
Joseph John Thomson
The plum pudding model of the atom by J. J. Thomson, who discovered the electron in 1897, was proposed in 1904 before the discovery of the atomic nucleus in order to add the electron to the atomic model. In this model, the atom is composed of electrons surrounded by a soup of positive charges. -
Robert Andrews Millikan
Millikan's Atomic Theory states that the mass of an electron is at least 1000 times smaller than the smallest atom. He came to this conclusion through the oil-drop experiment. In this experiment he created an atomizer. -
Ernest Rutherford
The Rutherford model is a model of the atom devised by Ernest Rutherford. Rutherford directed the famous Geiger-Marsden experiment in 1909 which suggested, upon Rutherford's 1911 analysis, that the so-called "plum pudding model" of J. J. Thomson of the atom was incorrect. Rutherford's new model for the atom, based on the experimental results, contained the new features of a relatively high central charge concentrated into a very small volume in comparison to the rest of the atom and with this ce -
Niels Bohr
In atomic physics, the Bohr model, introduced by Niels Bohr in 1913, depicts the atom as small, positively charged nucleus surrounded by electrons that travel in circular orbits around the nucleus similar in structure to the solar system, but with attraction provided by electrostatic forces rather than gravity. -
James Chadwick
James predicted the atom would have a neutron. He established that atomic number is determined by the numbers of protons in an atom. He also discovered the fourth subatomic particle,the neutron. -
Quantum Model
Scientists De Broglie, Heisenberg, Schrödinger made several works that we can't find exact place of electrons and their energy level. Electrons exist only in certain discrete energy levels which are described by quantum numbers. There are different orbital shapes such as S and P orbitals.
