History timeline of the atom

The History of the Atom

460-370 B.C

1897

1911

1913

History

Democritus was among one of the first people to describe an atom, this was called the billiard ball. He believed that the atom looked like a solid ball which could not be broken into anything smaller

Democritus

J.J Thompson

J. J Thompson discovered the electron, a very, very small particle that came out of atoms. Because the electrons had a negative charge he said that the rest of the atom must have a positive electric charge spread through out it. The atom is like a ball of positive electric charge with electrons dotted through it. This was called the Plum Pudding model

Earnest Rutherford discovered the nucleus. He fired alpha particles (which have a positive charge) at thin gold foil. Most particles went staright through the gold foil but some bounced back at Rutherford. He was amazed. The only explanation he could suggest that most of the atom was empty space and that all thepositive electric charge wasconcentrated in a very small part of the atom, which he called the nucleus. It was the nucleus which made the alpha particles to turn around andcome back. Calling this the Rutherford model.

Earnest Rutherford

Niels Bohr

Neils Bohr was a danish scientist that suggested that the electrons couln't just be anywhere around the neculeus. They had to be in certain fixed orbits. Calling this the Bohr model.