Which term is used to describe the horizontal rows on the periodic table?

• A. Families
• B. Periods
• C. Blocks
• D. Groups

Answer: (B)

Verified step by step guidance

1. Understand that the periodic table is organized in two main directions: horizontally and vertically.
2. Recognize that the vertical columns are called 'Groups' or 'Families', which contain elements with similar chemical properties.
3. Identify that the horizontal rows are called 'Periods'. Each period corresponds to the filling of a principal energy level of electrons.
4. Recall that 'Blocks' refer to sections of the periodic table based on electron subshells (s, p, d, f), not rows or columns.
5. Therefore, the term used to describe the horizontal rows on the periodic table is 'Periods'.