_____________________ go across the periodic table in rows.Group of answer choicesgroups/familesperiodsgas familyimposter families

The correct answer is "periods."

Explanation:

1. Definition of Periods: In the context of the periodic table, "periods" refer to the horizontal rows that organize the elements based on increasing atomic number. Each period represents elements with the same number of electron shells.

2. Characteristics of Periods:

   • As you move from left to right across a period, the atomic number increases, and the properties of the elements can change significantly.
   • Elements in the same period may exhibit different chemical behaviors and physical properties.

3. Contrast with Groups/Families: Unlike periods, "groups" (or families) refer to the vertical columns in the periodic table where elements share similar chemical properties and typically have the same number of electrons in their outer shell.

In summary, the periodic table is organized into rows called periods and columns known as groups or families.