Atomic Structure Timeline

Aristotle

340

Aristotle describes his idea of five elements of Matter. Aristotle believed that all matter was made up either of one of the elements of water air earth and fire or combinations of these four elements, with the exception of stars and planets which were made of aether

Democritus

460

Democritus developed the idea of an atom.

Antoine Lavoisier

Dec 10, 1774

Lavoisier observes that heating mercuric oxide produces metallic mercury.

John Dalton

Dec 10, 1802

He thus enunciated Gay-Lussac's law or J.A.C. Charles's law, published in 1802 came up with his own atomic theory.

Marie & Pierre Curie

Dec 10, 1894

They established that the heavy element thorium was radioactive and discovered two new elements: polonium and radium.

Henri Becquerel

Jan 1, 1897

Henri Becquerel researched the newly discovered X-rays it led to studies of how uranium salts are influenced by light.

J.J. Thomson

Dec 10, 1897

He discovered the atom.

Ernest Rutherford

Dec 10, 1899

He discovered alpha and beta rays

Max Planck

Dec 10, 1900

Max Planck discovered the quantum physics/theory.

Niels Bohr

Jan 10, 1913

Niels Bohr proposed a theory for the hydrogen atom based on quantumtheory that energy is transferred only in certain well defined quantities.

Henry Moseley

Dec 10, 1913

Observed the properties of x-rays from about a dozen consecutive elements in the periodic table. In doing so, he discovered that the wavelength of the x-rays became shorter as the atomic weight increased.

Robert Millikan

Dec 10, 1923

He discovered the charge and mass values or an electron.

Werner Heisenberg

Dec 10, 1925

Discovered a way to formulate quantum mechanics in terms of matrices.

Erwin Schrodinger

Dec 10, 1926

A powerful model of the atom was developed by Erwin Schrödinger.

James Chadwick

Dec 10, 1932

James Chadwick used scattering data to calculate the mass of this neutral particle to discover the neutron.