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Democritus
His atomic theory: all matter consists of invisible particles called atoms, atoms are indestructible, atoms are solid but invisible, atoms are homogenous, atoms differ in size, shape, mass, position and arrangement. solids are made of small, pointy atoms. Liquids are made of large, round atoms. Oils are made of very fine, small atoms that can easily slip by each other. -
Antoine Lavoisier
he pioneered the basics of stoichiometry by performing some of the first properly measured experiments. -
Antoine Lavoisier
he reformed chemical nomenclature, where instead of the classic elements he had named the (at the time) 55 things that could not be broken down any further. -
John dalton
he created the first model for atomic theory which contained 5 main points and depicted different atoms as different circles with symbols contained within them. -
Eugene Goldstein
discovered anode rays and sometimes is credited for discovering the proton. -
J.J. Thomson
He showed that cathode rays, radiation emitted in low pressure glass tube when a voltage is applied between two metal plates, consist of particles, that carry electricity. Thomson concluded that electrons were apart of the atom. Plum pudding model. -
Robert Millikan
he performed a oil-drop experiment to find the charge to mass ratio of an electron. -
Ernest Rutherford
Tested JJ Thomson theory on the atom by conducting the gold foil experiment. Thomson thought that the protons and electrons were uniformly spread through the atom. Rutherford proved him wrong and stated that the protons were in the center and the electrons orbited around them. -
Niels Bohr
he created the bohr model. Which was a model that depicts a positively charged nucleus surrounded by negatively charged electrons that in essence orbit around the nucleus. -
Henry Moseley
he proposed that the relationship was a function of the positive charge on the nucleus. This rearranged the periodic table by using the atomic number instead of atomic mass to represent the progression of the elements. This new table left additional holes for elements that would soon be discovered. -
James Chadwick
he showed that in the reaction between alpha particles against Beryllium, a neutral particle with the mass of about a proton was emitted.
