jan 1, 1911 - Ernest Rutherford's Model of the Atom
Rutherford decided to attempt to test Thomson's model. He did this by using radioactivity in an experiment using gold foil and a type of radiation named alpha particles. This led him to discover a dense positively charged core inside the atom called the nucleus. Rutherford then proposed that the nucleus is an extremely small, dense, and positively charged core of an atom, he also proposed that all of the positively charged particles in the atom, protons, are in the nucleus. He proposed that the nucleus is mainly surrounded by empty space and that negatively charged, electrons are spread out around the outside of the nucleus. This theory is now called the "nuclear" model.
Added to timeline:
The Atomic Theory