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Introduction In the beginning, the theory was prepared by Democritus dating back to the Greek era all the way to Enrico Fermi in 1942. Over twenty-five scientists have contributed to the theory throughout history. The modern theory of atomic structure includes information that all atoms are about the same size. There is a slight size change between the smallest and largest atom. Also the nucleus is the center of the atom. Protons are the positively charged particles making up the nucleus; and the neutrons have no charge and also are in the nucleus. Protons and neutrons are the two components that make up the weight of an atom. Surrounding the nucleus is the electron cloud. The electron cloud contains electrons which are negatively charged. Electrons weigh nothing. Each electron energy level follows definite orbital tracks. Each energy level has sublevels which follow certain orbital tracks. Chemists can use the theory to predict reactions between two or more elements. They can also predict what will happen during covalent or ionic bonding. The theory has changed many times throughout the years and is still changing presently. The theory was used by Mendeleev to construct the periodic table, another useful tool for chemists, and to help him predict some of the missing elements in his table. Just a few of the scientists that helped the atomic theory to be what it is today are: Democritus, John Dalton, Julius Plucker, Sir William Crookes, Amedeo Avagardo, Dimitri Mendeleev, Joseph John Thomson, Ernest Rutherford, Max Planck, Frederick Soddy, Hans Geiger, Ernest Marsden, Robert Andrews Millikan, Niels Bohr, Erwin Rudolf Josef Alexander Schrödinger, and Sir James Chadwick. Body Leucippus and his pupil, Democritus, are credited with hypothesizing the theory of Atoms and Void. Democritus expanded upon Leucippus' original theory and theorized on many of its detailed applications like perception. Democritus was a much more creative writer and is credited with writing fifty-two works, although some were quite short. Unfortunately, while his work on ethics comprised only a small portion of his work, nearly all the existing fragments from his work are from the ethical works. Dalton arrived at his view of atomism through the science of meteorology, in which he was seriously interested in for a long period. Dalton read a series of papers on meteorology that contained Dalton's independent statement of Charles' Law "All elastic fluids expand the same quantity by heat." In explaining the law of partial pressures to skeptical chemists of the day, Dalton claimed that the forces of repulsion thought to cause pressure acted only between atoms of the same kind and that the atoms in a mixture were indeed different in weight and "complexity." He proceeded to calculate atomic weights from percentage compositions of compounds, using an arbitrary system to determine the likely atomic structure of each compound.
Approximate Word count = 1723
Approximate Pages = 6.9
(250 words per page double spaced)
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