Chemistry: Atom Timeline

Democritus

400 BCE

Democritus created the atomic theory, that meant everything in the universe is made up of the following principle: everything is composed of atoms.

John Dalton

1803

Dalton came up with the atomic theory, 4 key points.

Dmitri Mendeleev

1869

Dmitri Mendeleev is known for working on the periodic law and creating the first periodic table.

Eugen Goldstein

1886

Goldstein was the first to observe the proton during his work with discharge tubes, observing rays going from cathode to anode, where he also noticed the presence of waves going in the opposite direction.

J.J Thomson

1897

Thomson discovered the electron in 1997, and then proposed the idea of the plum pudding model of the atom in 1904, in his model the atom was composed of electrons.

Robert Millikan

1909

Millikan is known for the Millikan Oil Drop, that determined the size of the charge on an electron.

Ernest Rutherford

1911

Rutherford is known for the creation of the Rutherford model of the atom, which showed that atoms have a small charged nucleus surrounded by open space, and are circled by tiny electrons. He was the first to discover that atoms have a nucleus

Max Planck

1918

Planck is known as the originator of the quantum theory of energy

Niels Bohr

1922

Bohr proposed a theory about the hydrogen atom based on the quantum theory that energy is only defined in well defined quantities.

Werner Heisenberg

1925

Werner Heisenberg is most commonly known for his uncertainty principle, and theory of quantum mechanics

Erwin Schrodinger

1926

Schrodinger used Mathematical equations to show to likelyhood of an electron being found in a certain position.

James Chadwick

1932

Chadwick discovered the neutron in atoms that contributed to the atomic weight of the atom.