Which of the following statements correctly describes a trend in atomic radii in the periodic table?

• A. Atomic radius decreases from top to bottom within a group.
• B. Atomic radius remains constant across a period.
• C. Atomic radius increases from top to bottom within a group.
• D. Atomic radius increases from left to right across a period.

Answer: (C)

Verified step by step guidance

1. Recall that atomic radius is the average distance from the nucleus to the outermost electron in an atom.
2. Understand the trend within a group (vertical column) of the periodic table: as you move from top to bottom, new electron shells are added, increasing the size of the electron cloud and thus the atomic radius.
3. Recognize the trend across a period (horizontal row): as you move from left to right, protons are added to the nucleus, increasing the nuclear charge, which pulls electrons closer and decreases the atomic radius.
4. Evaluate each statement based on these trends: atomic radius increases from top to bottom within a group, and atomic radius decreases from left to right across a period.
5. Conclude that the correct description is 'Atomic radius increases from top to bottom within a group,' while the other statements are incorrect.