 Any additional periods are expected to contain a larger number of elements than the seventh period, as they are calculated to have an additional so-called "g-block", containing at least 18 elements with partially filled g-orbitals in each period.An "eight-period table" containing this block was suggested by Glenn T. Seaborg in 1969.The first element of the g-block may have atomic number 121, and thus would have the systematic name unbiunium.