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Plato was the start of the atomic theory and theorized that matter, when solid, was composed of invisible triangle-shaped elements. -
Democritus believed that atoms were uniform, solid, hard, incompressible, indestructible, and that they moved in infinite numbers until they were stopped. -
The Alchemists believed that all metals were formed of Mercury and Sulfur and that by combining those two metals you could create any metal. -
In 1543 Nicolaus Copernicus created the solar system model, which tells of the relative position and motion of all the planets in the solar system. -
Robert Boyle believed that everything was made of the very tiny particles called atoms. -
Antone Lavoisier believed that during a chemical reaction atoms were neither created nor destroyed. -
In the early 1800's John Dalton created his billiard ball model. This model stated the atom was a ball-like structure. -
John Dalton believed that all elements were formed of invisible and indivisible particles called atoms. He also believed that all matter is made of these atoms. -
Amedeo Avogadro believed that gasses with equal volumes must also have an equal number of molecules and that elementary gasses (such as Hydrogen, Nitrogen, and Oxygen) are composed of two atoms. -
Dmitri Mendeleev is credited with creating the periodic table as we know it. -
JJ Thompson is credited with discovering the electron and he also proposed the structure of the atom. -
The Curies believed that radiation happened in the atoms, not on a molecular level. -
In 1904 JJ Thomson created his plum pudding model. This model stated that electrons were negatively charged particles suspended in a positively charged soup. -
Albert Einstein was able to use math to prove that atoms existed and showed that liquids are made of molecules. -
Robert Millikan is credited with discovering the charge an electron carried. -
Ernest Rutherford believed that atoms had a tiny, dense positively charged core, called the nucleus, where the mass of an atom is concentrated and that the electrons orbited around. -
Neils Bohr believed that electrons orbited the nucleus, but only in set orbits, and if an electron were to jump or change orbits it would cause an output of radiation. -
Henry G. J. Mosely discovered that an atom's atomic number is equal to the number of positive charges in the nucleus. -
Werner Heisenburg is credited with helping to create the mathematical models that predict the location of electrons. -
Erwin Schrödinger is credited with using mathematical formulas to determine the probability of finding an electron in a certain place. -
Erwin Schrödinger and Werner Heisenburg created the electron cloud model in 1926. This model stated that scientists could only calculate the likelihood of electrons being in a certain place, not actually find them. -
James Chadwich is credited with the discovery of the neutron.