History of Atomic Theories and Models

Events

Aristotle

442 BC

•He didn’t believe that everything is made up of atoms
•He instead believed in the four elements—water, air, and fire
•He thought that everything was made up of small quantities of these four elements

https://the-history-of-the-atom.wikispaces.com/Aristotle

Democritus

430 BC

• Created the first atomic model
• His model looked like a plain, circular sphere. It had no protons, neutrons, or electrons
•Believed that matter consisted of very small particles
•Called particles atoms or atomos meaning “invisible” in Greek

http://www.encyclopedia.com/people/philosophy-and-religion/philosophy-biographies/democritus

https://the-history-of-the-atom.wikispaces.com/Democritus

John Dalton

1803

•Developed the first atomic theory
•All matter is made of atoms and that atoms are invisible and indestructible
•Atoms of different elements combine in whole number ratios to form chemical compounds
•In a chemical reaction, atoms are combine, separated, or rearranged

http://www.iun.edu/~cpanhd/C101webnotes/composition/dalton.html

Sir William Crookes

1879

•First to prove the existence of cathode rays
•Discovered the element thallium
•Invented the radiometer, the spinthariscope, and Crookes tube
•Led to understanding of the subatomic structure of the atom

Joseph John Thomson

1897

Max Planck

1900

Albert Einstein

1905

Ernest Rutherford

1911

Neils Bohr

1913

Arnold Sommerfeld

1919

Louis de Broglie

1924

Werner Heisenberg

1925

Erwin Schrodinger

1926

James Chadwick

1932