Atomic Model Timeline

Democritus

400

Democratus claimed that everything is made up of atoms.

John Dalton

Oct 16, 1803

Theory states:
Matter is made up of atoms that are indivisible and indestructible
All atoms of an element are identical
Atoms of different elements have different weights and different chemical properties
Atoms of different elements combine in simple whole numbers to form compounds
Atoms cannot be created or destroyed

JJ Thomson

Oct 16, 1904

Thomson suggested a model of the atom as a sphere of positive matter in which electrons are positioned by electrostatic forces.

Ernest Rutherford

Oct 17, 1910

Rutherfords model described the atom as a tiny, dense, positively charged core called a nucleus, which nearly all the mass is concentrated, around which the light, negative constituents, called electrons, circulate at some distance, much like the planets revolving around the sun.

Niels Bohr

Oct 17, 1913

Bohr suggested that the electrons in an atom revolve around the nucleus of an atom only in certain discrete orbits with no other orbits being possible. That means that that an electron could occupyonly certain energy levels and that it must absorb or emit energy in discrete amounts as it moves from one allowed energy level to another.

Schroedinger

Oct 17, 1926

Schroedinger created the electron cloud model. This model assumes that the electron wave and tries to describe the regions in space, or orbitals, where the electrons could most likely be found.

Werner Heiserberg

Oct 17, 1926

Heiserberg calculated the behavior of electrons and subatomic particles that also make up an atom. His discovery helped clarify the modern view of the atom because scientists can compare the few number of atoms there are, by their movements of electrons, and how many electrons an atom contains.