History of the model of the Atom

Events

Democritus

400 B.C

Democritus’ atomic theory stated that all matter is made up small indestructible units he called atoms.

Isaac Newton

1704

Isaac Newton theorized a mechanical universe with small, solid masses in motion.

John Dalton

1803

John Dalton proposed that elements consisted of atoms that were identical and had the same mass and that compounds were atoms from different elements combined together.

J, Joseph Thomson

1897

J.J. Thomson determined the charge to mass ratio of electrons.

Ernest Rutherford

1898

discovered alpha, beta, and gamma rays in radiation.

Niels Bohr

1922

proposed an atomic structure theory that stated the outer orbit of an atom could hold more electrons than the inner orbit.

Lois de Brolie

1923

proposed that electrons have a wave/particle duality.

Werner Heisenberg

1925

Werner Heisenberg contributed to the atomic theory by including quantum mechanics, the branch of mechanics, based on quantum theory, used for interpretating the behavior of elementary particles and atoms.

Erwin Schrodinger

1926

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

discovered neutrons, particles whose mass was close to that of a proton.