The horizontal rows in the periodic table are called

The periodic table organizes elements in rows and columns. The horizontal rows going from left to right are called periods, numbered 1 through 7.

Each period represents elements with electrons filling the same outermost energy level. Period 1 has one energy level, period 2 has two, and so on.

Vertical columns are called groups or families because elements in the same column have similar chemical properties. Periods show how properties change across the table.