The horizontal rows of the periodic table are called periods.
As you can see in the image, the periodic table has 7 periods. As a side note, the vertical rows are called groups - there are 18 of those in the periodic
The horizontal rows on the periodic table are called periods.
The periodic table consists of seven rows called periods, and 18 columns called groups or families. The properties of the elements within a period vary across the periodic table in predictable ways, while the elements within a group have similar properties.