The Atomic Model Throughout Time

Democritus

370 BCE

Democritus, is recognized as the earliest source of the atomic theory. As opposed to popular opinion, Democritus believed that everything could be divided until there was a single base left. He believed that: this base could not be divided, was the material that created everything, that they had different shapes and sizes, and that different combinations created different types of matter. Thea image is a depiction of the various shapes of atoms.

Aristotle

332 BCE

Aristotle, an ancient Greek philosopher, had great influence over the people of Greece during his time. He popularized many beliefs and added credence to others. Specifically, Aristotle believed that everything, all matter, was made of four elements: Fire, Water, Earth, and Air. This was the popular opinion on the matter of what the matter that made up everything was, and of course, Democritus, the fellow philosopher who went on to disagree and come up with his own idea, was met with opposition.

John Dalton

1803

Dalton’s atomic theory contained five basic principles or assumptions. Dalton believed that 1) Atoms were what made up everything , 2) Atoms could not be created, destroyed, or changed into other atoms 3) The element that an atom is is dependent on the weight on the atom. 4) Atoms always combine in whole number ratios when they react chemically with one another, and 5) atoms can combine, while always whole numbers, can combine in other whole number ratios. The image depicts a solid sphere model

Sir Joseph John Thomson

1897

Sir Thomson, in 1897, executed the Cathode Ray Tube experiment where he found, with the knowledge that the catahode rays were negativley charged, that the atoms had some form of negative charge but also a positive charge given that they did not react towards the ends of the ray in a straight line. Thomson’s atomic model is one that he likened to plum pudding, thus the nickname, where the electrical charges in the atom are scattered throughout the atom and surrounded by a positive charge.

Ernest Rutherford

1911

The image depicts a proton in the center with electrons speckled around it. + is positive - is negative.

Neils Bohr

1913

The image depicts a proton in the center and electrons orbiting around it on tracks. + is positive - is negative, o are orbital tracks.

Erwin Schroedinger

1926

The image depicts a proton in the center with an electron cloud. + is positive, gray is cloud.

Modern Model

1932

James Chadwick

1932

The image depicts neutron+proton nucleus and electrons surrounding them. += positive -= negative other is neutral.