The Evolution of the Atomic Model

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Dalton

1800

Developed an early atomic theory named after the scientist.

Thomson

1897

Using a discharge tube, discovered that negatively charged particles called electrons are inside the atom and also found that all atoms have the same kind of electrons (demonstrated by the raisin bun model.)

Rutherford

1900

A student of Thomson's, used radium to conduct a gold foil experiment and found that the atom had a very dense core called a nucleus. He also discovered that electons revolved around the nucleus.

Bohr

1913

This Danish scientist found that electrons that orbited the nucleus also occupied specific energy levels. He also discovered for an electron to move from one energy level to a higher level, it had to absorb a specific amount of energy called a quantum. He demonstrated his findings by creating the Bohr-Rutherford model.

Scientific Findings

1928

Several scientists identified the positive charges in the nucleus as protons.

James Chadwick

1932

Showed (via experiments) the presence of neutrons.