The aim is to reveal a new rule that governs Periodic Table. The basis of study is also the Periodic Table that organizes the elements by their atomic number, their electronic configuration, and their properties. The method is to analyze Noble Gase’s atomic number sequence and try to find a formula that explains this sequence. The consequences of this new rule led us to understand “Octet Rule” is nothing more than the initial part of a broader rule that truly governs the development of Periodic Table and therefore the behavior of the atom and chemistry itself. From the new rule, we can also deduce atom shape and electronic configuration, as well as how atom expands its nucleus with new protons to form new elements.