John Dalton developed the atomic theory which stated; all matter is made up of atoms, all atoms of a given element are the same, compounds are formed by 2 or more different atoms combining, and in particular compounds elements always combine in the same way.
1897 - J.J. Thomson
Thomas showed atoms were made of even smaller particles by discovering electrons. His model of the atom is know as the plum pudding model.
1904 - Hantaro Nagaoka
Nagaoka proposed a model of the atom in which positively charged center is surrounded by revolving electrons.
1911 - Ernest Rutherford
Rutherford concluded the atom is 99.99% empty space; the nucleus contains a positive charge and most of the atoms mass.
1913 - Niels Bohr Model
In the Bohr model the atom is depicted as a small positively charged nucleus surrounded by electrons that travel in circular orbits.
1924 - Louis de Broglie
De Broglie suggested mabey electrons are actually little waves going around the nucleus.
1926 - Erwin Shrodinger
Shrodinger developed the cloud model which says there is no way to tell were the electron is at any point but were it should be.
1932 - James Chadwick
Chadwick discovered the neutron by firing alpha particles at beryllium and a beam with high penetration power was created.