Timeline: History of the Atom by: Irene Valenzuela

Sep 3, 1803

Atomic Model

Sep 4, 1803

John Dalton

-In 1803 he developed the first useful atomic theory of matter. His atomic theory makes the assumptions that all matter consists of tiny particles, atoms are indestructible or unchangeable, and elements are characterized by the mass of their atoms, when elements react, their atoms combine in simple, whole-number ratios, and that when elements react, their atoms sometimes combine in more than one simple, whole-number ratio.

Sep 4, 1861

William Crookes

In 1861 he discovered the element thallium. He also developed the Crookes tubes. In his investigations of the conduction of electricity in low pressure gases, he discovered that as the pressure was lowered, the cathode appeared to emit cathode rays, now known to be a stream of free electrons, and used in cathode ray display devices.

Sep 4, 1897

J.J Thomson

In 1897 he discovered the electron in a series of experiments designed to study the nature of electric discharge in a high vacuum cathode ray tube.

Sep 4, 1904

Thomson's Atomic Model

In 1904 he suggested the model of the atom as a sphere of positive matter in which electrons are positioned by electrostatic forces.

Sep 4, 1911

Ernest Rutheford

In 1911 he theorized that atoms have their own charge concentrated in a very small nucleus. He made the Rutherford Model through his discovery and interpretation of Rutherford scattering in his gold foil experiment.

Sep 4, 1911

Rutheford Model

Sep 4, 1913

Niels Bohr

In 1913 he suggested that electrons could only have certain classical motions.

Sep 4, 1913

Bohrs Model

-In 1913 he introduced the Bohr’s model, this model shows the atom as a small, positively charged nucleus surrounded by electrons that travel in circular orbits around the nucleus.

Sep 4, 1926

The Quantum Mechanical Model

The modern description of the electrons in atoms, the quantum mechanical model, comes from the mathematical solutions to the Schrodinger equation. It was created in 1926.