-
400 BCE
Democritus
He was a Greek philosophern (460 B.C. -370 B.C.) that discovered the existence of the atom. He believed that atoms were indivisible, but he did not have any experimental support. -
John Dalton
He was an English chemist and school teacher ( 1766-1844) He used atomic experimental methods to transform Democritus's ideas about atoms into the atomic theory. -
Eugen Goldstein
German physicist (1850-1930). He discovered anode rays and is sometimes credited with the discovery of the proton. -
JJ Thompson
English physicist (1856-1940). He performed experiments (cathode-ray tube) that involved passing electric currents through gasses under pressure. The cathode was made up of electrons. He discovered the "plum pudding model". -
Ernest Rutherford
He was a former student of Thompson (1871-1937). He tested the theory of atomic structure. He used a narrow beam of alpha particles directed at a very think sheet of foil. This was called the Gold-Foil experiment. This helped discover the atomic nucleus. -
Nieles Bohr
He was a Danish physicist (1885-1962). He changed Rutherford's model. He proposed that an electron is found in only circular paths or the electrons orbit around the nucleus. Proposed that the electron orbit has a fixed energy which are called energy levels. -
Erwin Shrodinger
Austrian physicist (1887-1961). Solved the equation that described the behavior of the electron in a hydrogen atom. The modern description of this model is called the quantum mechanical model. -
Louis De Broglie
French physicist (1892-1987). He found that electrons can have waves and he suggested that all matter had wave properties. -
James Chadwick
English physicist (1891-1974). He discovered the neutron and he directed alpha particles at nuclei
