Atomic Model

Empedocles

440 BCE

Empedocles suggested that there were four elements: Water, Earth, Air, and Fire. It seemed logical because when things caught fire, moisture is released, air can be felt coming up from it, and the ashes show the earth that it contained.

Democritus

400 BCE

A Molecular Dynamics simulation. About 400 B.C. the Greek philosopher Democritus suggested that all matter was formed of different types of tiny discrete particles and that the properties of these particles also determined the properties of matter.

Joseph Priestly

1774

discovered oxygen in 1774, he answered age-old questions of why and how things burn. An Englishman by birth, Priestley was deeply involved in politics and religion, as well as science

John Dalton

1803

In an article John Dalton wrote for the Manchester Literary and Philosophical Society in 1803, Dalton created the first chart of atomic weights.

Michael Faraday

1830

Michael Faraday was an English scientist who contributed to the fields of electromagnetism and electrochemistry. His main discoveries include those of electromagnetic induction, diamagnetism and electrolysis

Robert Millikan

1868

Robert Millikan was a physicist who discovered the elementary charge of an electron using the oil-drop experiment.

J.J. Thomson

1897

In 1897, J.J. Thomson discovered the electron by experimenting with a Crookes, or cathode ray, tube. He demonstrated that cathode rays were negatively charged. In addition, he also studied positively charged particles in neon gas.

Marie & Pierre Curie

1898

Marie & Pierre Curie In 1898, they announced the discovery of two new elements, radium and polonium.

. Ernest Rutherford

1911

Ernest Rutherford discovered the nucleus of the atom in 1911.

Niels Bohr

1913

In 1913, Niels Bohr proposed a theory for the hydrogen atom based on quantum theory that energy is transferred only in certain well defined quantities. Electrons should move around the nucleus but only in prescribed orbits. When jumping from one orbit to another with lower energy, a light quantum is emitted.

Erwin Schrödinger

1926

Erwin Schrödinger an Austrian physicist, took the Bohr atom model one step further. Schrödinger used mathematical equations to describe the likelihood of finding an electron in a certain position. This atomic model is known as the quantum mechanical model of the atom.

James Chadwick

1932

Chadwick is best known for his discovery of the neutron in 1932. A neutron is a particle with no electric charge that, along with positively charged protons, makes up an atom's nucleus. Bombarding elements with neutrons can succeed in penetrating and splitting nuclei, generating an enormous amount of energy.