Atomic Theory Timeline

Events

Leucippus

480 BC - 420 BC

Theorized that matter is homogeneous, consisting of small indivisible particles, called atoms which are constantly in motion, and form compounds via collisions. This could be considered the first atomic theory.

Democritus

460 BC - 370 BC

Democritus developed Leucippus's atomic theory. He theorized that atoms had space in between each other, were indivisible, and could not be destroyed.

First Atomic Theory

Approx. 400 BC

Aristotle

384 BC - 322 BC

Disagreeing with Democritus, Aristotle believed that the world was made of 4 elements: air, water, fire, and earth. This was perhaps the first theory that elements existed.

Isaac Newton

January 4, 1643 - March 31, 1727

Proposed a mechanical universe where small solid masses were in motion.

Benjamin Franklin

1706 - 1790

Proposed matter had positive and negative charges after his famous kite flight is 1752

Antoine Lavoisier

1743 - 1794

Stated the first law of conservation of mass in 1789.

John Dalton

September 6, 1766 - July 27, 1844

Discovered the atom in 1803

Michael Faraday

September 22, 1791 - August 25, 1867

Discovered method of splitting molecules using electricity in 1832, later making laws of electrolysis

Julius Plucker

June 16, 1801 - May 22, 1868

In 1859, built first functioning cathode ray, which was later used to theorize that atomic particles each contained certain charges.

William C. Roentgen

March 27, 1845 - February 10, 1923

Discovered that x-rays could pass through solid objects in 1895.

Henri Becquerel

December 15, 1852 - August 25, 1908

Discovered some chemicals spontaneously decompose and give off penetrating waves.

J.J. Thomson

December 18, 1856 - August 30, 1940

Found electrons and isotopes, in 1906 was awarded nobel peace prize for discovery of the atom.

Marie Curie

November 7, 1867 - July 4, 1934

Discovered radioactivity in 1898

Robert Milikan

March 22, 1868 - December 19, 1953

Discovered the charge and mass of an electron in 1909

Ernest Rutherford

August 30, 1871 - October 19, 1937

His Rutherford model in 1911 theorized that atoms were mostly empty, known as "the father of nuclear physics".

Albert Einstein

March 14, 1879 - April 18, 1955

First to show a way to prove the existence of atoms.

Niels Bohr

October 7, 1885 - November 18, 1962

Created the Bohr model in 1913, with electrons orbiting around a central nucleus.

Erwin Schrodinger

August 12, 1887 - January 4, 1961

Proposed electrons behaved in the matter of an electron cloud.

James Chadwick

October 20, 1891 - July 24, 1974

Discovered neutron in 1932, and theorized the neutron exists to stabilize the atom.

Louis de Broglie

August 15, 1892 - March 19, 1987

Dicovered that electrons behaved like waves under certain conditions.

Werner Heisenberg

December 5, 1901 - February 1, 1976

Created the Uncertainty Principle, stating that the exact location and energy of an electron cannot be determined simultaneously.

Peter Higgs

May 29, 1929 - September 24, 2017

Theorized the Higgs Boson Particle A.K.A. the god particle, in 1964.