The first periodic table published by D. I. Mendelejeev in 1869 based on atomic masses and had empty positions that paved the way for the discovery of several new elements. With the discovery of Pu by Glenn Seaborg as a transuranium element a worldwide race for synthesis of new elements started, mostly at LBNL (Berkeley, USA) and JINR (Dubna, Russia), later also at GSI (Darmstadt, Germany) and at RIKEN (Japan). Currently, 118 elements are known and approved by IUPAC. The heaviest is Oganesson completing the 7th period of the periodic table. While all elements up to Md have been discovered by chemists, heavier ones were found in physics experiments. Chemical experiments have so far reached atomic number 114 (Fl). Efforts are actually made to extend the periodic table into the 8th period starting with element 119. The ultimate limit of the periodic table is predicted at atomic number 172 being the heaviest element with a stable electron shell structure.