The periodic table has seven officially recognized periods.
A period is a horizontal row in the table. The seven periods correspond broadly to the successive principal energy levels occupied by electrons, although the details become more complex as subshells fill. Period 1 contains only hydrogen and helium, while later periods contain progressively more elements.
Periods 2 and 3 each contain eight elements. Periods 4 and 5 each contain 18, and periods 6 and 7 each contain 32 positions when the lanthanides and actinides are included. The f-block elements are often displayed below the main body to keep the table compact, but they belong to periods 6 and 7.
Periods are different from groups, which are the vertical columns. The modern table has 18 groups and seven periods. A chart may visually separate the f-block, but that presentation does not create extra periods.