-
460 BCE
Democritus
Idea for the atom -
John Dalton
Thought that atoms were small solid particles that could not be subdivided -
JJ Thompson
Discovered the electron and proposed the plum-pudding model of the atom, which was a solid ball with electrons sticking to the surface of that ball, also proven to be wrong.
-
Ernest Rutherford
Made another model of the atom by conducting the gold foil experiment in 1911. This experiment proved against Thompson’s atomic model. He showed that the atom had a tiny nucleus in the middle, with the electrons orbiting around the nucleus. This experiment was done using alpha particles from radioactive materials as probes for his studies with gold atoms. -
Niels Bohr
Made the model of the atom that we use today, a nucleus at the center, with various sized electron shells holding a set amount of atoms. -
Quantum Theory
Quantum theory gave the atomic theory the idea of the existence of the electron cloud, which states that electrons orbit the nucleus in a cloud, not in specific rings. Each electron has a probability of being in an energy level, or shell, meaning that an electron does not have a specified place around the nucleus.