----Atomic+Models(lm)

The Electron had come about in the 1920’s. This model was a mix of all of the past models from Democritus, Dalton, Thomson, Rutherford, and Bohr. Erwin Schrodinger and Werner Heisenburg discovered the functions that were involved in determining the regions of clouds where the electrons would be. The Electron Cloud Model describes how the nucleus composed of protons and neutrons surrounded by electrons that exist in different clouds at the various energy levels. Electrons are at different energy levels, scattered around the nucleus. [] []
 * The Electron Cloud Model **

The Plum Pudding Model was constructed by JJ Thomson. This Model was proposed in 1904 before the discovery of the atomic nucleus. Thomson had also had previously discovered the electron in 1897. In this model, the atom is composed of electrons. It resembles a soup of positive charge to balance the electron's negative charge, like negatively-charged “plums” surrounded by positively-charged “pudding”. This model was proven untrue in 1911 by Rutherford’s Gold Experiment that had a very small nucleus of the atom containing a very high positive charge (enough to balance about 100 electrons in gold), thus leading to the Rutherford Model of an Atom. [|**http://www.absoluteastronomy.com/topics/Plum_pudding_model**] [|**http://library.thinkquest.org/28582/history/plum.htm**]
 * The Plum Pudding Model **

In the year 1912 Neils Bohr joined up with Ernest Rutherford to combine both of their knowledge. First Rutherford had come up with a new discovery about the atom. He knew after his gold foil experiment that atoms were made up mostly of empty space with scattered negatively charged electrons scattered about. When Bohr had got word of the discovery he realized that the idea would be unstable in the rules of physics. Bohr then went on to make a new theory using quantum numbers, and came to the conclusion of how many electrons could be held on a shell, 2,8,10,14. Also elements that have the same number of electrons on the outermost shells appear in the same column in the periodic table.
 * Rutherford-Bohr model **

[]

Planetary model [] The planetary model, also known as the Bohr model, portrays the atom with a small super dense nucleus in the center of the particle with the electrons orbiting much the same way our planets do. In the atom the attractive force comes from the electric force between the positive nucleus and the negative electrons, however the planets are held in orbit around the sun due to gravity. The planetary model was used from 1915 to 1926 when the electron cloud model replaced it. []

Small spherical solid model [] The theory of the small spherical solid atom states that everything is made up of matter and space. All matter is made up of atoms. The atoms are small solid spherical particles that cannot be destroyed, and therefore cannot be created.

Losi.Mcneil.Atomic.Historytimeline.fall.2009