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Plato came up with elements. He believed in the five different forms of elements; wood, fire, earth, metal, and water. -
Democritus made a theory posited that matter is all made up of small indestructure units called atoms. -
The Alchemists started the belief that all metals were formed from two principles: mercury and sulfur -
The Solar System Model is a model of atoms as the consisting of a nucleus with a number of electrons in orbit around that nucleus. -
Robert Boyle focused on the study of gases. He proposed that elements are composed of "corpuscles" of various sizes and can organize themselves in groups. -
Antone Lavoisier grouped elements as substances: gases, metals, non-metals, and physical and chemical substances. -
John Dalton proposed that compounds were atoms from different elements combined together and that are consisted of atoms that are identical and have the same mass. -
The Billiard Ball Model was the finding that an atom is to be a ball-like structure. It concepts of the atomic nucleus and electrons. -
Amadeo Avogadro discovered equal volumes do gases at the same temperature and pressure contain the same number of molecules. -
Dmitri Mendeleev created the periodic table. He made the discovering of different elements easy to categorize. -
JJ Thompson determined the charge to mass ratio of electrons. -
Pierre and Marie Curie discovered polonium and radium, which helped us understand radioactivity. They discovered that polonium and radium gave off tiny atoms tat disintegrated inside elements. -
The Plum Pudding Model is an atom with a positive and negative charge. It's the finding that an atom is made like a sphere with a positive charge but has negatively charged electrons embedded in it. -
Albert Einstein proposed the quantum of light in which he states that light is like a particle and has a wave nature that is giving a dual nature. He also started the equivalence of energy and mass through the theory of special reactivity. -
Robert Millikan discovered the charge of an electron with his oil drop experiment. -
Ernest Rutherford discovered a small, dense, positively charged nucleus as the result of the alpha particles scattering gold foil experiment. -
Neils Bohr proposed an atomic structure theory, that stated that the outer orbit of an atom could more electrons than the inner orbit. -
Henry G. J. Mosely made the discovering of number of protons in an element and its atomic number. -
Werner Heisenberg discovered the uncertainty relation. He formulated a type of quantum mechanics based on matrices. -
Erwin Schrödinger studied the behavior of electrons within atoms. Which could be explained by treating them mathematically as matter waves. -
The Electron Cloud Model is a model showing how electrons move in a cloud. It's the region of negative charges, which surrounds the nucleus. -
James Chadwich discovered that there are neutrons in an atom which helped understand the building blocks of atoms.