Founding Fathers Dozens of brilliant minds contributed to our understanding of the atom. Below, a list of selected individuals  with their contributions to the atomic theory and quantum mechanics John Dalton (1766-1844):     John Dalton was an English scientist studying chemistry, physics, and meteorology. He coined the atomic theory stating: elements are made of atoms, atoms of the same elements are identical, they cannot be subdivided nor created, atoms can combine elements to form compounds,  and are rearranged in chemical reactions. Much of his theory is accurate and contributed to what we know today even though he wasn't entirely correct. Dimitri Mendeleev (1834-1907):     Dimitri Mendeleev was a Russian chemist who is responsible for the periodic table we have today. There were only 56 known elements when he began his research. He identified many properties of the known elements, organized them in a fairly accurate table, and even helped discover and predict the discovery of other elements. Eugene Goldstein (1850-1930):     Eugene Goldstein was a German physicist who discovered the presence of protons through in the atom. Using discharge tubes, which were also called Crookes tubes, he observed the glow of atoms when exposed to magnetic fields to prove his theory. J.J. Thomson (1856-1940):     Sir Joseph Thomson was an English physicist who used a similar approach and method to that of Eugene Goldstein to discover the presence of electrons and that their mass is much smaller than that of the nucleus. He used cathode rays to do so and proved that the rays were made up of the unknown negative particles. Ernest Rutherford (1871-1937):     Ernest Rutherford was a physicist from New Zealand that disproved the plum pudding model of the atom by revealing the atom is composed of a small nucleus with space around it. He shot particles through a very thin sheet of gold and observed that many of the particles shot right through while other deflected to prove the theory he proposed. He also helped found nuclear science. James Chadwick (1891-1974):     James Chadwick was an English physicist that discovered the presence of a neutral particle in the atom known as the neutron. His discovery was crucial to nuclear science and he went on to be a part of the Manhattan Project during WW2 which studied and developed the use of nuclear bombs. Albert Einstein (1879-1955):     Albert Einstein was a German physicist who could be considered the father of quantum mechanics. He was responsible for the theory of relativity and also developed one of the most well known equations, "E=mc^2). He identified that particles can have wave-like properties as well.