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460 BCE
Democritus
Democritus created the atomic model and started thinking of atoms as minuscule quantities of matter making up all things. -
322 BCE
Aristotle
Aristotle didn't believe in atomic theory, contradicted his teacher, and instead proposed all things are made up of fire, water, air, and earth. -
Lavoisier
Lavoisier created the Law of Conservation of Mass, the total mass of the products of a chemical reaction is always the same as the total mass of the starting materials consumed in the reaction. -
Dalton
John branched off of aristotle's ideas and explained all things are made up of atoms and that atoms cannot be split into smaller pieces. Dalton also proposed the theory, all atoms of the same element are exactly alike and different elements are made up of different elements are made of different atoms. -
Mendeleev
Mendeleev created the periodic table and created a format for how to classify each element and how to arrange them in the periodic table. -
Thomson
Created the plum pudding model. Thomson proposed electrons are negatively charged and unknown positive charges. He thought the atom was positively charged, but negatively charged electrons were spread evenly among it. If the atom has more positive mass, the proton is positively charged, negative mass, the proton is negatively charged. -
Millikan
Millikan determined that the electron was negatively charged and demonstrated the atomic structure of electricity. -
Rutherford
Rutherford created a new atomic model with electons revolving around the nucleus, and said the atom has an atomic nucleus containing protons and neutrons. -
Bohr
Bohr theorized that electrons orbit the nucleus in a predetermine route and that electrons jump to a lower-energy orbit, the difference is sent out as radiation. -
Chadwick
Chadwick discovered neutrons, the unknown positive charge earlier theorized, and discovered particles that had mass similar to proton.