Atomic Theory Timeline

Democritus

460

Developed the theory of atoms. He stated they were indivisible particles of matter that make up the entire universe

John Dalton

Jan 1, 1803

The scientist John Dalton rebirthed Democritus's ancient theory of atoms by performing experiments. He stated atoms were spherical balls of matter that were in constant motion

J.J. Thompson

Jan 1, 1897

Discovered the electron and proposed a model of the atom. It looked like a chocolate chip cookie with the dough being the positive charge, and the chocolate chips being the electrons.

Ernest Rutherford

Jan 1, 1911

Used his famous gold foil experiment to discover the proton, and theorize that electrons rotate around the nucleus.

Neils Bohr

Jan 1, 1912

Theorized that electrons rotate on different levels and they can jump from level to level.

Schrodinger

Jan 1, 1926

Created the theory of the electron cloud, saying that electrons don't orbit like planets.

Ernest Orlando Lawrence

Jan 1, 1929

Created the theory of "smashing atoms" by using an electromagnet to accelerate nuclear particles.

Cockroft and Walton

Jan 1, 1930

Used artificially accelerated particles to split an atom.

Electron Microscope

Jan 1, 1931

German egineers Ernst Ruska and Max Knoll used J.J. Thompson's theory of electrons to create a microscope powered by a particle beam of electrons.

James Chadwick

Jan 1, 1932

Stated that a gamma ray experiment, done by French scientists to see if they shot alpha particles at light atoms if a penetrating radiation was produced, was untenable. He concluded that a sub-atomic particle with no charge and mass equal to a proton was the cause.

Calutron

Jan 1, 1942

Using his theory of smashing atoms, Ernest O. Lawrencecreated the calutron, a device that seperated uranium-235 from uranium hexaflouride.

Atomic Bomb

Jan 1, 1945

Using Cockroft and Walton's discovery of splitting and atom, Robert Oppeinheimer and a team of scientists developed the atomic bomb.