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467 BCE
Democritus
Theorized all material bodies are made of indivisibly small "atoms", one of the first if not the first atomic theory. -
427 BCE
Plato
Theorized everything broke down into atomic triangles, which was very similar to our modern-day understanding of atoms -
122 BCE
The Alchemists
Thought elements sulfur & mercury created all metals, had a basic understanding of microscopic elements which were pretty close to modern day atomic theory -
Robert Boyle
His corpuscularian hypothesiss was one of the first atomic theory. It states that everything is made up of tiny particles called corpuscles, later known as atoms. -
Antoine Lavoisier
Antone Lavoisier's Law of Conservation of Matter helped John Dalton establish his atomic theory -
John Dalton
Created atomic theory & proposed the billiard ball model.
His atomic theory state that all matter is comprised of atoms with different compositions, like atoms now. The billiard ball model was just a sphere, as at the time there was no understanding of protons, electrons, and neutrons. -
Amedeo Avogrado
Established that same volumes of different gases contain equal molecules, showing that all atoms have a relatively same size, and created a constant which we use in every calculation for atoms today. -
Dmitri Mendeleev
Invented a periodic table so good that he managed to predict multiple elements that were not discovered prior. -
Pierre & Marie Curie
Proved the existence of positively, neutrally, and negatively charged subatomic particles, which helped find protons, neutrons, and electrons. -
JJ Thomson
Discovered the electron, which he then proposed the plum-pudding model. The plum pudding model is a bunch of detached electrons in a positively charged body. -
Albert Einstein
Proved the existence of atoms, making sure that all of the atomic theory is true. -
Robert Millikan
Proved the existence of electrons, helping formulate lots of types of atom diagrams -
Ernest Rutherford
Proved the existence of the atomic nucleus, which is used in lots of atomic models now -
Henry G. J. Mosely
Concluded atomic number to be the amount of protons in an atom, which were the properties of the atom. Helped future scientists not to confuse atoms to be the same by their mass. -
Niels Bohr
Proposed the electrons orbit around the nucleus of an atom, which then proposed the Bohr's model of an atom which is widely used today. Depicted either by the solar system (planetary) model or the electron cloud model. -
Erwin Schrödinger
Increased the precision of calculating atom energy levels, making sure that the property is correctly measured -
Werner Heisenberg
His uncertainty principle states that an electron can only be moving at a set speed, which is a property of an atom. -
James Chadwich
Proved the existence of neutrons, explaining why the mass of some atoms are more than the amount of protons in the atom.