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500 BCE
The Alchemists
They Discovered a material that would alter common metal into silver or gold. -
428 BCE
Plato
A Greek philosopher that came up with these 4 elements fire, water, earth, and air. -
400 BCE
Democritus
Atomic Theory stated that all matter's made of small indestructible units called atoms. -
Robert Boyle
Regarded today as the first modern chemist and one of the founders of modern chemistry. -
Antone Lavoiser
French chemists invented the first periodic table which had three elements. He also named hydrogen and oxygen. -
Billiard Ball Model
Discovered by John Dalton. Saying atoms were the smallest particles of matter. -
John Dalton
Stated all elements consisted of atoms that were identical had the same mass, and compounds were atoms from different elements combined. -
Amadeo Avagadro
He stated that equal volumes of gases at the same temperature and pressure contain equal numbers of molecules. -
Dmitri Mendeleev
Created the Periodic Table. Known as the Father of the Periodic Table. -
JJ Thompson
Create a charge to matter ratio of electrons. -
Plum Pudding Model
Discovered by J J Thompson. He said atoms were spheres of positive electricity with negative particles throughout. -
Pierre and Marie Curie
They discovered radioactivity and two new elements on the periodic table which consist of Radium and Polonium. -
Albert Einstein
He proved the existence of atoms and said that any liquid is made up of molecules. -
Robert Millikan
Found the change of an electron with his oil drop test or experiment. -
Ernest Rutherford
Finished a tiny dense, positively charged nucleus as the result of the alpha particles scattering gold foil experiment. -
Neils Bohr
He was a physicist who established an atomic structure theory that said the outer orbit of an atom could hold more electrons than the inner orbit. -
Henry G. J. Mosely
Found the number of protons in an element and its atomic number. -
Electron Cloud Model
Discovered by Erwin Schrodinger and Werner Heisenberg. Stated an atom consists of a dense nucleus and many proton and neutrons and are surrounded by electrons, but all atoms have different energy levels in different charges. -
Solar System Model
Rutherford and Bohr contributed to this model. Rutherford said the atom is mainly empty space with a nucleus that has a positive charge surrounded by negative electrons. Also, Bohr said they circulate the atom. -
Erwin Schrodinger
He created wave and quantum mechanics. -
Werner Heisenberg
He discovered a key piece of quantum theory which is the uncertainty principle stating particles' position and momentum can't both be known fully. -
James Chadwich
He discovered neutrons and particles.
