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In 500 B.C, the Alchemists discovered a substance that would change the more common metals into silver or gold. They eventually failed to turn the items into gold, but they created a scientific process which would lead to the discovery of the atom. -
In 428 B.C, Plato came up with elements and was also convinced that atoms must from five fundamental solids. -
Democritus was an ancient greek philosopher that in 400 B.C created a theory that stated that matter is made up of small indestructible units that were called atoms. -
Robert Boyle talked about the possibilities of atoms existing, and he mainly studied gases. He proposed that elements are composed of particles of different sizes and types that can be able to organize themselves into groups that represent different chemical substances. -
In 1777, Antone Lavoisier, a french man, found that in a chemical reaction, mass is conserved. We understand now that matter is conserved because atoms are neither created or destroyed in a chemical reaction. -
In 1803, John Dalton thought that compounds were atoms from different elements combined together and are made up of atoms that are the same and also had the same mass. -
The Billiard Ball Model was created by John Dalton in 1807, and he saw the atoms as hard, solid spheres. -
In 1811, Amedeo Avogadro reasoned that simple gases were compound molecules of two or more atoms instead of being formed by solitary atoms. -
In 1869, Dmitri Mendeleev created the periodic table of elements. -
In 1897, JJ Thomson created an experiment that showed that tiny negatively charged particles are in all atoms. -
In 1898, Marie and Pierre Curie discovered two radioactive elements called polonium and radium. Marie created the term radioactivity for the spontaneous discharge of ionizing, penetrating rays by certain atoms. -
The Plum Pudding Model was created by JJ Thomson in 1904. It shows how the atom is a sphere of positive charge, and negatively charged electrons are in there too to balance the total positive charge. -
In 1905, Albert Einstein proved the existence of atoms mathematically. Through the theory of special relativity, he was able to start the equivalence of energy and mass. -
Robert Millikan made an oil drop experiment which resulted in the discovery of the charge of an electron, in 1908. -
In 1909, Ernest Rutherford discovered that the atom is made up of mostly empty space and that the atom's mass is concentrated in its nucleus. -
In 1913, Neils Bohr suggested an atomic structure theory that mentioned that the outer orbit of an atom could hold more electrons than the inner orbit. He also realized that the electrons did not crash into the nucleus. -
Ernest Rutherford and Niels Bohr created the Solar System Model which is a system that contains tiny, dense nucleus surrounded by orbiting electrons. It was created 1913. -
In 1914, Henry G.J. Mosely discovered that the number of positive charges in the atomic nucleus is the atomic number. -
In 1926, Erwin Schrödinger described the likelihood of finding an electron in a certain position by using mathematical equations. -
The Electron Cloud Model was created by Erwin Schrödinger in 1926 and it shows a certain area where an electron is most likely to be. -
In 1927, Werner Heisenberg discovered the uncertainty principle that states that we can't know, with perfect accuracy, the position and speed of a particle. -
In 1932, James Chadwick discovered the neutron. This discovery eventually led to the development of the atomic bomb.