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Period: 460 BCE to 370 BCE
Democritus
Democritus was a Greek philosopher that believed that atoms were different shapes and sizes, that they were indivisible and indestructible. The model of the atom that he created was solid.
Atom Model -
Period: to
John Dalton
Dalton's theory included that everything was made of atoms. It also included that different atoms of different materials have a different size and mass. He also believed that atoms of different elements combine in simple whole numbers. Atoms are combined, separated or rearranged but are never changed.
Dalton's Model -
Period: to
Dmitri Mendeleev
Mendeleev created the first Periodic Table.
Mendeleev's Table -
Period: to
Eugene Goldstein
Goldstein discovered that there were protons in an atom, and they were positively charged
Goldsteins Model -
Period: to
J.J Thomson
Thomson discovered the electron, and thought they were positioned in the atom in rotating rings.
Thomson's Model -
Period: to
Max Planck
Planck discovered that energy is emitted from a black body in discrete amounts called quanta. He showed that the amount of energy was proportional to the frequency of the radiation that was absorbed by the black body, a relationship now known as Planck's Law. Planck's Model -
Period: to
Robert Millikan
Millikan came up with a series of experiments to determine the electric charge carried by a certain electron.
Millikan's Model -
Period: to
Ernest Rutherford
Rutherford discovered that the atom has a nucleus, and that the nucleus is small, dense, and positively charged.
Rutherford's Model -
Period: to
Niels Bohr
Bohr proposed that energy levels of electrons are discrete and that the electrons revolve in stable orbits around the atomic nucleus but can jump from one energy level to another.
Bohr's Model -
Period: to
Erwin Schrodinger
Schrodinger used math equations to find the describe the likelihood of finding an electron in a certain position.
Schrodinger's Model -
Period: to
James Chadwick
Chadwick discovered that there was a neutron in the nucleus of an atom. The neutron has no charge.
Chadwick's Model -
Period: to
Werner Heisenberg
Heisenberg came up with the theory that an atom has electrons in fixed orbits around a nucleus.
Heisenberg's Model
