Date: 460-370 BC

Associated experiment: NA (theoretical)

Description of model: Composed of tiny particles. The particles take on the physical properties of the object.

Thomson 

Date: 1897 (published on April 30, 1897) 

Associated experiment: Thomson used cathode rays to discover the electron. 

Description of model: Thomson's model is called the "Plum Pudding Model," it shows the atom as a big ball of positive charge with tiny negative electrons mixed in, like plums in a pudding. 

Date:1911

Associated Experiment: Rutherford used Dalton and Thomson idealogy/experiment combined into his experiment.

Description of Model: Dots are the path of the alpha particles, with a very thin gold foil in the middle, and a circle of screen coated with ZnS which glows green when hit by charged particles, and a shielded source of alpha particles on the left side. The path of alpha particle changes.

Date: 1808

Associated Experiment: Used electricity to split water in hydrogen and oxygen gas and he weighed each of them separately and found that oxygen is always 8 times heavier than hydrogen. With that result, he came up with the law of definite proportions. 

Description of model: He thought elements were small, indestructible atoms each of unique proportions, size, and mass. He also said atoms could not be created. His idea of the shape of an atom was a sphere with a thin layer of positive charge in which there is electrons stuck between

Date: 1920s to present

Associated experiment: contributors include Werner Heisenberg, Max Planck, Erwin Schrödinger, Wolfgang Pauli and many others), many different experiments conducted.

Description of the model: The atom contains a small, dense positive nucleus surrounded by electrons that travel in a wave-like motion around the nucleus. This motion is modified by mass and charge interactions between electrons and the nucleus. The interactions and the fast speed of the electron make it impossible to know with any certainty both where an electron is and where it is going in any particular instant. All we can know is the general area of space in which the electron might be found. They very from the most general location to the most specific.

Date:1913

Associated ExperimentRutherford’s Gold Foil Experiment (Used to develop his theory and develop the model) 

Franck-Hertz Experiment (Used to prove Bohr’s theory and model) 

Description of the Model:

The atom has 2 parts, the nucleus and electric shells. The electric shell circles the Nucleus with different numbers of electrons in each ring. The nucleus contains Neutrons and Protons.  

-->Erwin Schrödinger, who formulated the wave mechanics equation in 1926, built on the concept of electrons behaving as waves, which was first proposed by Louis de Broglie-->the idea of electrons orbiting on fixed shells was changed and now perceived as 3d probability clouds in orbitals. That means that electrons now dont have a specific range of movement, but we can only know the approximate location of them.

->Current model: Quantum Mechanical Model