There are 7 periods in the periodic table. A period is a horizontal row of elements, and each period corresponds to the filling of a principal energy level with electrons. The first period has 2 elements, periods 2 and 3 have 8 elements each, periods 4 and 5 have 18 elements each, and periods 6 and 7 have 32 elements each due to the inclusion of the lanthanides and actinides
. Thus, the modern periodic table consists of seven horizontal rows called periods. Any new elements discovered beyond the current 118 would begin an eighth period
