How the Atomic Theory developed over time

Democritus B.C.

400

This is Democritus' atomic theory exactly: 1.All matter consists of invisible particles called atoms.

1. Atoms are indestructible.
2. Atoms are solid but invisible.
3. Atoms are homogenous.
4. Atoms differ in size, shape, mass, position, and arrangement.

->Solids are made of small, pointy atoms. ->Liquids are made of large, round atoms. ->Oils are made of very fine, small atoms that can easily slip past each other.

Aristotle. B.C.

500

John Dalton

Jan 1, 1830

Dalton's Atomic Theory 1) All matter is made of atoms. Atoms are indivisible and indestructible. 2) All atoms of a given element are identical in mass and properties 3) Compounds are formed by a combination of two or more different kinds of atoms. 4) A chemical reaction is a rearrangement of atoms.

J.J. Thomson

Jan 1, 1897

In this model, the atom is composed of electrons surrounded by a soup of positive charge to balance the electrons' negative charges, like negatively-charged "plums" surrounded by positively-charged "pudding".

Hanaro Nagaoko

Jan 1, 1904

The model made two predictions: 1.) a very massive nucleus (in analogy to a very massive planet)
2.) electrons revolving around the nucleus, bound by electrostatic forces (in analogy to the rings revolving around Saturn, bound by gravitational forces).

Ernest Rutherford

Jan 1, 1911

In 1911, he theorized that atoms have their positive charge concentrated in a very small nucleus and thereby pioneered the Rutherford model of the atom, through his discovery and interpretation of Rutherford scattering in his gold foil experiment. He is widely credited with first "splitting the atom" in 1917 in a nuclear reaction between nitrogen and alpha particles, in which he also discovered (and named) the proton.

Niels Bohr

Jan 1, 1913

Louis de Broglie

Jan 1, 1924

Erwin Schrodinger

Oct 31, 1926

James Chadwick

Oct 31, 1932