Period 1 element Period 1 element A period 1 element is one of the chemical elements in the first row (or period) of the periodic table of the chemical elements. The periodic table is laid out in rows to illustrate periodic (recurring) trends in the chemical behaviour of the elements as their atomic number increases: a new row is begun when chemical behaviour begins to repeat, meaning that elements with similar behaviour fall into the same vertical columns. The first period contains fewer elements than any other row in the table, with only two: hydrogen and helium. This situation can be explained by
Extended periodic table periodic table would quite possibly end around "Z" = 130. Beyond element 164, the fissility line defining the limit of stability with respect to spontaneous fission may converge with the neutron drip line, posing a limit to the existence of heavier elements. Nevertheless, further magic numbers have been predicted at "Z" = 210, 274, and 354 and "N" = 308, 406, 524, 644, and 772, with two beta-stable doubly magic nuclei found at 210 and 274; the same calculation method reproduced the predictions for Fl and 164. Although additional stability toward alpha decay and fission are predicted for these nuclei,