Which of the following best describes the trend in atomic radius as you move from left to right across a period on the periodic table?

• A. Atomic radius increases
• B. Atomic radius decreases
• C. Atomic radius first increases, then decreases
• D. Atomic radius remains constant

Answer: (B)

Verified step by step guidance

1. Recall that atomic radius refers to the size of an atom, typically measured as the distance from the nucleus to the outermost electron cloud.
2. Understand that as you move from left to right across a period in the periodic table, the number of protons in the nucleus increases, which increases the nuclear charge.
3. Recognize that the increased nuclear charge pulls the electrons closer to the nucleus because the electrons are added to the same principal energy level, so shielding effect remains relatively constant.
4. Because the electrons are pulled closer to the nucleus, the atomic radius decreases across a period from left to right.
5. Therefore, the best description of the trend in atomic radius across a period is that the atomic radius decreases.