Atomic Model

Democritus

460

Created the first atomic model.His model of the atom depended on analogies from human senses. The atomic theory posited that all matter is made up small indestructible units he called atoms.

Timeline of the Atomic Model

Period: 460 to Oct 30, 1932

Democritus

Jan 1, 1764

Democrtitus said that all matter consists of extreamly small particles, which can not be seperated what so ever. He called these small things atoms. There is no evidence of experiments.

Daltons theory

Oct 30, 1803

All atoms of an element were identical and that in particular they had the same mass.He also said that the reason elements differed from one another was that atoms of each element were different from one another; in particular, they had different masses.
1. Matter is made up of atoms that are indivisible and indestructible. 2. All atoms of an element are identical. 3. Atoms of different elements have different weights and different chemical properties. 4. Atoms of different elements combine in s

J.J. Thomas

Dec 18, 1856

He discovered the Plum Pudding Model of the atom.In J.J.'s model, the atom is composed of electrons surrounded by an area of positive charges to balance out the negative charges.He thought that electrons are embeddded in a sphere made of posistive electric charge.

Max Planck

Apr 23, 1858

Planck contibuted to the atomic theory by saying that energy can only be emitted in discrete chunks. His expeirimented by observing light emitted by a heated object at various temperatures. This theory was called the theory of quanta.

Neil Bohr

Oct 7, 1885

Niel Bohr's model was not completely correct, but it had many features that are approximately correct . It said that the electrons move in spherical orbits around the nucleous at fixed speeds and fixed distances. He based this on the planets orbiting aound the sun.

Henry Moseley

Nov 23, 1887

Moseley found a relationship between an element's X-ray wavelength and its atomic number. His discovery showed that atomic numbers had an experimentally measurable basis. He used X-ray wavelengths to help him with the contribution.

Ernest Marsden

Nov 1, 1909

He discovered the existence of the atomic nucleus.He discovered this by using the Gold Foil Experiment or the Rutherford Experiment.

Erwin Schrödinger

Oct 31, 1926

He generated a mathematical model for the distribution of electrons in an atom.He combined the equations for the behavior of waves with the Louis de Broglie equation.

James Chadwick

Oct 31, 1932

He proved the existence of neutrons.He heard of a new method of detecting particles emitted by radioactive elements developed by Irene Joliot-Curie.