History of the periodic table managed to get thallium, lead, mercury and platinum into the right groups, which is something that Mendeleev failed to do at his first attempt. Odling failed to achieve recognition, however, since it is suspected that he, as Secretary of the Chemical Society of London, was instrumental in discrediting Newlands' earlier work on the periodic table. By 1912 almost 50 different radioactive elements had been found, too many for the periodic table. Frederick Soddy in 1913 found that although they emitted different radiation, many elements were alike in their chemical characteristics so shared the same place on the table. They became
Extended periodic table due to its much higher atomic weight. Unseptbium should be a strong Lewis acid, forming fluorides and oxides, similarly to its lighter congener xenon. Because of this analogy of elements 165–172 to periods 2 and 3, Fricke et al. considered them to form a ninth period of the periodic table, while the eighth period was taken by them to end at the noble metal element 164. This ninth and final period would be similar to the second and third period in that it should have no transition metals. Immediately after element 172 (unseptbium, the last period 8 element), the first