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460 BCE
Democritus
The greatest contribution of Democritus in astronomy is the atomic theory-the belief that everything in the world consists of particles called atoms. These atoms, Democritus believed, are indestructible, indivisible, and always in motion. They atoms are infinite in numbers, and come in different sizes and shapes. -
427 BCE
Plato
Plato postulated that a fifth atomic type must exist which Aristotle later called `ether'. The heavens, and objects in the heavens are composed of atoms of ether. This is perhaps the first example of the use of theoretical thought experiments to predict or postulate new concepts. -
340 BCE
Aristole
The contribution Aristotle made to the Atomic theory was that he believed in the four elements of air, earth, water and fire. Aristotle felt that regardless of the number of times you cut a form of matter in half, you would always have a smaller piece of that matter. -
500
The Alchemists
The alchemists began examining the atomic theory about two centuries after the death of Aristotle. They used Aristotle’s idea about matter and began to create experiments and activities with them. By treating different metals and ores, the goal was to change the structure of the item so that it could become more valuable. Although the alchemists failed to turn common items into gold, they did create a scientific process which would allow for the eventual discovery of the atom. -
Robert Boyle
Robert Boyle is known as “The Father of Chemistry” for his discovery that atoms must exist based on the relationship between pressure and volume of gas. His theorem called Boyle’s Law reasons that because a fixed mass of gas can be compressed, gas must be made of particles, or atoms, because there is space between them. -
Lavoisier
Antoine Lavoisier after the French Revolution, was a French nobleman and chemist who was central to the 18th-century chemical revolution and who had a large influence on both the history of chemistry and the history of biology. He is widely considered in popular literature as the "father of modern chemistry". -
John Dalton
John Dalton contributed a lot to the atomic theory. He was the first scientist to explain the behavior of atoms in terms of the measurement of weight. He also revealed the concept of Dalton's Law of Partial Pressures in 1803.He is best known for introducing the atomic theory into chemistry. -
Solid Sphere of "Billiard Ball" Model
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Dmitri Mendeleev
Dmitri Mendeleev's Contribution to Atomic Theory is He developed the periodic table. Scientific Rewards. He organized the elements into a table according to their atomic weights. When the elements were arranged in ascending order in their weights, their properties repeated in a pattern. -
J.J. Thomson
J.J. Thomson is credited with the discovery of the electron, the negatively charged particle in the atom. He is known for the Thomson atomic theory. Many scientists studied the electric discharge of a cathode ray tube. It was Thomson's interpretation that was important. -
The Curies
The theory of radioactive decay proposed by Curie helped in validating the existence of subatomic particles. It was found that by emitting energy and electrons, atoms can undergo changes and lead to the rise of completely new atoms. The discovery of polonium and radium strengthened this theory, as both elements were found to be highly radioactive. -
"Plum Pudding" Model
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Albert Einstein
In 1905 Einstein contributed three papers to Annals of Physics, a German scientific periodical. Each of them became the basis of a new branch of physics. Einstein treated matter and energy as exchangeable. Albert Einstein became famous for the theory of relativity, which laid the basis for the release of atomic energy. -
Ernest Rutherford
Experiments & contribution to atomic theory Rutherford discovered that placing Uranium near foil resulted in one type of radiation being easily soaked up or blocked, while a different type had no trouble penetrating the same foil. He labeled the two radiation types “alpha” and “beta.” -
Robert Millikan
Robert Millikan's primary contribution to atomic theory came as a result of his oil-drop experiment, which measured an electron's charge. Previously, J.J. Thomson had suggested the hypothesis that an electron's mass was at least 1,000 times less than the mass of the tiniest atom. Millikan's contribution to this hypothesis was to specify the size of the electron's charge. -
Neils Bohr
Niels Bohr applied his atomic theory to the periodic table of elements. He showed that chemical properties of an element resulted mainly from the behavior of valence electrons, the electrons occupying the highest stable orbit. -
Solar System Model
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Henry G.J. Mosely
Henry Moseley, in full Henry Gwyn Jeffreys Moseley, (born November 23, 1887, Weymouth, Dorset, England—died August 10, 1915, Gallipoli, Turkey), English physicist who experimentally demonstrated that the major properties of an element are determined by the atomic number, not by the atomic weight, and firmly established the relationship between atomic number and the charge of the atomic nucleus. -
Werner Heisenberg
Heisenberg's contributions to the atom are that he calculated the behavior of the electrons around the atom with the Uncertainty Principle. Heisenberg changed the way people look at atoms now because he helped clarify the amount of electrons to determine how many electrons an atom contains. -
Electron Cloud Model
