Which term describes a horizontal row of elements in the periodic table?

Which term describes a horizontal row of elements in the periodic table?

• A. Period
• B. Group
• C. Family
• D. Row

Answer: (A)

A horizontal row on the periodic table is called a period. As you move from left to right within a period, the same outer-shell level (same principal energy level) is being filled while the number of protons and electrons increases. That’s why the table is arranged in horizontal rows by increasing atomic number. The vertical columns are groups or families, which is why those terms describe sets of elements with similar chemical properties due to their valence electrons. So the formal term for a horizontal row is period.

A horizontal row on the periodic table is called a period. As you move from left to right within a period, the same outer-shell level (same principal energy level) is being filled while the number of protons and electrons increases. That’s why the table is arranged in horizontal rows by increasing atomic number. The vertical columns are groups or families, which is why those terms describe sets of elements with similar chemical properties due to their valence electrons. So the formal term for a horizontal row is period.