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

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

Answer: (A)

Verified step by step guidance

1. Understand that atomic radius refers to the size of an atom, typically measured as the distance from the nucleus to the outermost electron cloud.
2. Recall 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 the shielding effect remains relatively constant.
4. Conclude that this stronger attraction between the nucleus and electrons causes the atomic radius to decrease across a period.
5. Therefore, the best description of the trend in atomic radius from left to right across a period is that the atomic radius decreases.