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Democritus a Greek philosopher, believed that the universe was made of empty space and tiny bits of stuff. He called these tiny bits of stuff “atoms.” He believed that different types of atoms existed for every type of matter.
Antoine Lavoisier a French chemist, conducted a series of experiments involving chemical reactions, proving that matter could not be created or destroyed, it only changed form; law of conservation of matter.
John Dalton an English chemist, introduced an early atomic theory of matter.
J.J. Thomson an English physicist, discovered negatively charged electrons using a cathode ray tube.
Ernest Rutherford a New Zealand-born English physicist, conducted his gold foil experiment; discovered the positively-charged center of the atom—the nucleus, as well as discovered positively charged protons; determined that atoms were mostly empty space.
James Chadwick a student of Rutherford’s, discovered neutral (meaning “no charge”) neutrons in the nucleus of an atom. His proton-neutron model of the atomic nucleus is still accepted today.
Niels Bohr a Danish physicist, proposed that electrons were located in specific energy levels and that electrons traveled in definite orbits around the nucleus. His atomic model is often called the “planetary model.”
Dmitri Mendeleev a Russian chemist, created the first periodic table that was arranged by increasing atomic mass.
Created by: S730503