Davidsons Atomic Model

Democritus

Jan 1, 1000

Democritus believed that matter consisted of very small particles, which he called atoms, that can't be divided. He also thought that there were different types of atoms that haad specific properties.

Aristotle

Oct 28, 1000

Aristotle did not believe that there was a limit to the number of times that matter could be divided. In order to do this, he experimented many times.

John Dalton

Sep 6, 1766

John Dalton gathered evidence for the existence of atoms. He did thisby measuring masses of elements that combine when compounds are formed. Also, heconcluded that a gas conisists of individual particles. John Dalton said that all matter is made up of individual particles called atoms.

J.J Thomson

Dec 18, 1856

J.J Thomson hypothesized that a sealed glowing beam with gas at low pressure was a stream of charged partriclesthat interact with the air in the tube which caused the air to glow. He used an electric current to learn more about atoms. His experiments provided the first evidence that atoms are made of smaller particles.

Hantaro Nagaoka

Aug 15, 1865

Nagaoka believed that an atom has a central nucleus and that they move in orbits like the rings around saturn.

Rutherford

Aug 30, 1871

Rutherford discoverd that uranium releases fast-moving particles that have a positive charge. In order to prove this, he aimed a narrow beam of alpha particles at gold.

Neils Bohr

Oct 7, 1885

Bohr developed diagrams of an atom that look like a solar system. The "planets" revolve around a "sun". He created a model that focused on electrons.

Schrödinger

Aug 12, 1887

Schrödinger developed a math equation to explain motions of electrons in atoms. This created the electron cloud model.

Ernest Marsden

Feb 19, 1889

Ernest Marsden was one of Rutherfords students. Rutherford asked him to find out what happens to alpha particles when they pass through a thin sheet of gold.

James Chadwick

Oct 20, 1891

James Chadwick confirmed the existence of neutrons. In order to prove this, he attcaked the alpha rays coming out of radioactive material on a Beryllium atom and observed the results. He discovered that Beryllium becomes radioactive for a short time and releases material rays containing neutral particles.

Louis de Broglie

Aug 15, 1892

Broglie believed that moving particles have some properties of waves. His ideas were supported.

Heisenberg

Dec 5, 1901

Heisenberg created the Uncertainty Principle, which stated that the accuracy with which properties of atoms and particles can be determined simultaneously. He also invented the first version of the Matrix Mechanics.

Bernard Pullman

Mar 19, 1919

Pullman created a new field of Quantum Biochemistry. He also predicted the carcinogenic properties of aromatic hydrocarbons.