nucleus, which is surrounded by mainly empty space, which contains the electrons. In 1914 Rutherford made up the word “proton,” which were subatomic particles that had a positive charge. A student of Rutherford’s, a man named H. G. J. Moseley was the one who gathered the empirical support for Rutherford’s work. In his experiments he used X-rays to show that the positive charge in the nucleus grows by one, from each element to the other. From this Moseley devised the concept of Atomic Number. In 1932, James Chadwick established that the nucleus must contain heavy neutral particles as well as positive ones, this was to explain the entire mass of the atom. He called the neutral subatomic particles neutrons. I Danish scientist named Niels Bohr created a theory explaining the periodic law. Bohr took the Quantum Theory of Energy, proposed by Max Planck (in 1900), and the relationship between the sudden end of the periodic table. Using this, periodic law, and some experimental evidence, Bohr hypothesized the following: - Each electron has a fixed quantity of energy related to the circular orbit in which the election is found. - Electrons cannot exist between orbits, but they can move to unfilled orbits if a quantum of energy is absorbed or released. - The higher the energy level of an electron, the further it is from the nucleus. - The maximum number of electrons in the first three energy levels is 2, 8, and 8. - An atom with a maximum number of electrons in its outermost level is stable, that is, it is unreactive. Bohr’s theory was developed mathematically, so as to explain the visible spectrum of hydrogen gas, as well as to predict other lines of ultraviolet and infrared light. One of the great things about Bohr’s theory is that it explains periodic law. The theory states that properties of elements can be explained by the way that their electrons are arranged. Due to the fact that orbits can only contain...
