Extended periodic table The next six elements on the periodic table should be the last main-group elements in their period. In elements 167 to 172, the 9p and 8p shells will be filled. Their energy eigenvalues are so close together that they behave as one combined "p" shell, similar to the non-relativistic 2p and 3p shells. Thus, the inert pair effect does not occur and the most common oxidation states of elements 167 to 170 should be +3, +4, +5, and +6 respectively. Element 171 (unseptunium) is expected to show some similarities to the halogens, showing various oxidation states ranging from −1 to
Extended periodic table recent discovery being that of tennessine in 2010. As some superheavy elements were predicted to lie beyond the seven-period periodic table, an additional eighth period containing these elements was first proposed by Glenn T. Seaborg in 1969. This model continued the pattern in established elements and introduced a new g-block and superactinide series beginning at element 121, raising the number of elements in period 8 compared to known periods. These early calculations failed to consider relativistic effects that break down periodic trends and render simple extrapolation impossible, however. In 1971, Fricke calculated the periodic table up to "Z" = 172,