Extended periodic table table. The table below shows one possibility for the appearance of the eighth period, with placement of elements primarily based on their predicted chemistry. All of these hypothetical undiscovered elements are named by the International Union of Pure and Applied Chemistry (IUPAC) systematic element name standard which creates a generic name for use until the element has been discovered, confirmed, and an official name approved. These names are typically not used in the literature, and are referred to by their atomic numbers; hence, element 164 would usually not be called "unhexquadium" (the IUPAC systematic name), but rather "element 164" with
Extended periodic table and discovered that some elements indeed had different properties that break the established pattern, and a 2010 calculation by Pekka Pyykkö also noted that several elements might behave differently than expected. It is unknown how far the periodic table might extend beyond the known 118 elements, as heavier elements are predicted to be increasingly unstable. Glenn T. Seaborg suggested that the highest possible element may be under "Z" = 130, while Walter Greiner predicted that there may not be a highest possible element. There is currently no consensus on the placement of elements beyond atomic number 120 in the periodic