All matter is made of atoms. In 470 BC Democritus suggested that a substance can be cut over and over to get to the tiniest piece of that substance that contains all of the properties of the larger piece. In doing so, he proposed the existence of an atom. The word atom comes from the Greek word “atomos” which means not-cut. Aristotle, an influential thinker, rejected the idea of the atom. Since his teachings were revered, the concept of the atom was lost for 2,000 years. In 1803, John Dalton resurrected the concept of the atom. Lord Rutherford refined the concept of atoms by explaining that atoms consist largely of empty space. After conducting his Gold Foil Experiment, Rutherford deduced that all atoms had a small dense positively charged center portion of particles (protons) and stated that negatively charged particles (electrons) surround the nucleus of positively charged particles and take up most of the space of the atom. Niels Bohr (Rutherford’s student) refined Rutherford’s planetary model of the atom by suggesting that electrons must exist in fixed paths or orbits. The Modern Model uses Bohr’s idea of energy levels for electrons but does refer to the direct path of the electron. Instead, it speaks about the probability of finding an electron in a certain position

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