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500 BCE
The Alchemists
Discovered a substance that would transmute the more common metals into silver or gold -
428 BCE
Plato
Plato came up with elements -
400 BCE
Democritus
The theory posited that matter is all made up of small indestructible units called atoms -
Robert Boyle
Discussed the possibilities of atoms existing he studied mainly gases he proposed that elements are composed of "corpuscles" of various sizes and types that can be able to organize into groups that represent different chemical substances -
Antone Lavoisier
French Chemist who proved conservation of matter and also explained the mysteries of fire -
John Dalton
Proposed that compounds were atoms from different elements combined together and consisted of atoms that were identical and also had the same mass -
Billiard Ball Model
Dalton at the time thought atoms were the smallest particles of matter and envisioned them as solid hard spheres -
Amedes Avogadro
The equal volumes of gases at the same temperature contain equal numbers of molecules. -
Dimitri Mendeleev
Created periodic table -
JJ Thompson
J.J determined the charge to mass ratio of electrons -
Pierre and Marie Curie
They discovered polonium and Radium -
Plum Pudding Model
Negatively charged electrons are surrounded by positively charged which was proposed by J.J Thompson -
Albert Einstein
Proposed the quantum of light in which he states that light is like a particle and also has a wave nature that is giving a dual nature. Also started the equivalence of energy and mass through the theory of special relativity -
Robert Millikan
Discovered the charge of an electron with his oil drop experiment -
Ernest Rutherford
Concluded a small dense positively charged nucleus as the result of the alpha particles scattering gold experiment -
Solar System Model
Ernest Rutherford proposed that atoms are act like a solar system -
Neils Bhor
Proposed an atomic structure theory that stated the outer orbit of an atom could hold more electrons than the inner orbit -
Henry G.J Mosely
Henrey discovered that the number of protons in an element an its atomic number -
Werner Heisenberg
Had the theory of quantum mechanics -
Erwin Schrodinger
Erwin formulated a wave equation that accurately calculated the energy levels of electrons in atoms. -
Electron Cloud Model
The model explains that we can't know where the electron is at any given time but the electron sare more likely in the specific areas proposed by Erwin Schrodinger -
James Chadwich
James proved the existence of neutrons