Alternative periodic tables quantum numbers of the electron configuration, hence it has a four-dimensional base. In Theodor Benfey's periodic table (1964), the elements form a two-dimensional spiral, starting from hydrogen, and folding their way around two peninsulars, the transition metals, and lanthanides and actinides. A superactinide island is already slotted in. The Chemical Galaxy (2004) is organized in a similar way. Timothy Stowe's physicist's periodic table is three-dimensional with the three axes representing the principal quantum number, orbital quantum number, and orbital magnetic quantum number. Helium is again a group 2 element. Paul Giguère's 3-D periodic table consists of 4 connected billboards with
Extended periodic table have a metallic radius of only 158 pm, very close to that of the much lighter magnesium, despite its expected atomic weight of around 474 u which is about 19.5 times the atomic weight of magnesium. This small radius and high weight cause it to be expected to have an extremely high density of around 46 g·cm, over twice that of osmium, currently the most dense element known, at 22.61 g·cm; unhexquadium should be the second most dense element in the first 172 elements in the periodic table, with only its neighbor unhextrium (element 163) being more dense (at 47