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DemocritusDemocritus was the man that first discovered what an atom, he lived from 460BC to 370BC. Democritus's theory was that matter could not be divided into smaller and smaller pieces forever, eventually the smallest possible piece would be obtained. This piece would be indivisible. He named the smallest piece of matter “atomos,” meaning “not to be cut.”
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The years starting with the creation of the Atomic theory then throughout history of various scientists discovering more in depth theories about atoms.
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DaltonJohn Dalton lived from 1766-1844. He is known for discovering that all matter is made up of atoms, atoms are indivisible and indestructible, all atoms of a given element are identical in mass and properties, compounds are formed by a combination of two or more different kinds of atoms, a chemical reaction is a rearrangement of atoms, and atoms can be neither created nor destroyed.
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ThomsonJ.J Thomson lived from 1856-1940. He is known for creating a modle of an atom which is called the plum pudding model. His modle suggested that an atom consisted of electrons and protons.
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RutherfordErnest Rutherford lived from 1871-1937. He discovered that the atom must have almost all of its mass concentrated at its center, in a nucleus, with the vast majority of the atom consisting chiefly of empty space.
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BohrNiels Bohr lived from 1885–1962. He refined Rutherford's model in 1913 by proposing that electrons can orbit the nucleus without losing energy, could move only in fixed orbits of specific energies. Electrons with low energy would orbit closer to the nucleus while electrons with high energy orbit further from the nucleus.
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BroglieLouis de Broglie lived from 1892 – 1987. He suggested that, like light, electrons could act as both particles and waves. De Broglie's hypothesis was soon confirmed in experiments that showed electron beams could be diffracted or bent as they passed through a slit much like light could.
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ChadwickJames Chadwick lived from 1891-1974. He identified the nuetron, with the discovery of the neutron three subatomic particles were identified that would help explain observations made at the atomic level.
