Periodic Table and Atomic Structure

Events

Democritus

442 BC

Democritus theorizes an indivisible particle which he names the atomos.

John Dalton

1803

Expanded on Democritus's theory.

Johan Dobereiner

1817

Dobereiner creates law of triads.

John Newlands

1864

Newlands creates law of octaves.

Dmitri Mendeleev

1869

Mendeleev organises elements by atomic mass and properties, creating the framework for the periodic table we see today.

Lothar Meyer

1870

Meyer had ideas similar to Mendeleev, but was afraid to publish them. He made a graph that listed the relations between atomic mass and number.

Lord Rayleigh

1894

DIscovered the noble gas argon with Ramsey.

William Ramsay

1894

Discovered argon with Rayleigh and went on to discover other noble gases.

J.J Thompson

1897

Created plum pudding model.

Ernest Rutherford

1909

Created the Rutherford model where electrons rotated around a positive nucleus.

H.G Mosely

1913

Discovered that amount of protons equals atomic number.

Niels Bohr

1913

Created planetary model.

James Chadwick

1932

Discovered neutrons.

Glenn Seaborg

1940

Discovered trans-uranium elements and discovered isotopes.