In the periodic table, what are the rows and columns called?

• A. Rows are called groups, and columns are called periods.
• B. Rows are called families, and columns are called periods.
• C. Rows are called blocks, and columns are called families.
• D. Rows are called periods, and columns are called groups.

Answer: (D)

Verified step by step guidance

1. Understand the layout of the periodic table: it is organized in horizontal rows and vertical columns.
2. Identify the terminology for the horizontal rows: these are called \textbf{periods}. Each period corresponds to the filling of a different electron shell.
3. Identify the terminology for the vertical columns: these are called \textbf{groups} or sometimes \textbf{families}. Elements in the same group have similar chemical properties because they have the same number of valence electrons.
4. Recall that the terms 'blocks' refer to sections of the periodic table based on electron subshells (s, p, d, f), not rows or columns.
5. Therefore, the correct naming is: \textbf{rows are called periods} and \textbf{columns are called groups}.