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Thales
Thales was an ancient Greek philosopher that transformed the abstract theories of others into solid concepts of his own. His theories were accepted long after his death and contributed to the growth of the Atomic Model.He believed that water was the basis of all material. He lived from 624 B.C. until 547 B.C. -
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Kanada, Acharya
Acharya Kanada came up with idea of the Atomic Theory. He believed everything that was in existence fitted into one of nine elements: Earth, Water, Light, Wind, Ether, Time, Space, Mind and Soul. He was an Indian philosopher and sage who lived in the 7th century B.C. -
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Aristotle
Aristotle expanded on other theories on the four elements, Fire, Water, Earth and Air, saying that there were qualities that fitted in between the elements; hot, wet, dry & cold. Aristotle was born in 384 B.C. and died in 322 B.C. -
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Democritus
Democritus’ theory was that everything was made up of atoms, a term that he came created. He stated many fact on these atoms such as; that atoms are indestructible; are always in motion; and that there were infinite numbers of atoms.He also stated "The more any indivisible exceeds, the heavier it is.” but this theory on the mass of atoms is now disputed. He lived from 460 B.C. to 370 B.C. -
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Aristotle's Atomic Model
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Empedocles
Empedocles lived from 490 B.C. until 430 B.C. in Greece. Empedocles narrowed Kanada’s theory of nine elements in the Universe to four; Air, Water, Earth and Fire. He also stated that there were two forces, love/eros and hate/strife, which determined how the four elements combined or separated. -
Antoine Lavoisier
Antoine Lavoisier is famous for many things such as stating the first law of mass conversion, recognizing and naming oxygen and hydrogen, writing the first large list of elements and for helping create the metric system.He also discovered that mass always stays the same even when the matter changes shape. He was beheaded on the 8th of May 1794. -
Joseph Proust
Joseph Proust came up with the Law of Definite Proportions. This Law said that chemical substances can combine to create a number of small compounds, each different in weight. This theory wasn’t accepted but was later and still is to this day. He died on July 5, 1826. -
John Dalton
John Dalton conceived the idea of atoms. He said that atoms of different elements are different to each other in ways such as size, mass & other properties. He believed that you couldn’t destroy or create atoms and that the only way to combined separate or rearrange atoms was by a chemical reaction. He also stated that atoms from different elements could combine easily to create a compound.He died on the 27th of July 1844. -
Joseph John Thomson
Joseph John Thomson came up with the “plum pudding theory”. This theory stated that the neutrons and protons were like the pudding part of the plum pudding and the electrons were like the fruit, spread out through corpuscles. He died on the 30th of August 1940. -
Robert Millikan
Millikan conducted an experiment called the Oil Drop Experiment that helped him determine the charge of electrons. He died on December 19, 1953. -
Ernest Ruttherford
Rutherford proved that J.J. Thomson’s theory was wrong and that the protons and neutrons were group in the middle of the atom in a nucleus and that the electrons orbited the nucleus.He did this by firing alpha particles through a sheet of gold foil. If Thomson’s theory was corrected then nearly all the alpha particles would bounce back. But instead hardly any bounced back, leading him to his theory about the nucleus.He died on the 19th of October 1937. -
Erwin Schrödinger
Schrödinger said that electrons weren’t distributed win an electron configuration of shells and energy levels and instead were in orbitals that were in an Electron Cloud. He died on the 4th of January 1961. -
James Chadwick
James Chadwick discovered the neutron in 1932. He discovered that neutrons were just heavier than protons and carried no electrical charge. This discovery explained why the total mass of the atom was larger than the mass of the protons and electrons. He died on July 24th, 1974.