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

Answer: (A)

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 although electrons are added as you move across a period, they are added to the same principal energy level, so the shielding effect does not increase significantly.
4. Because the increased nuclear charge pulls the electron cloud closer to the nucleus without much additional shielding, the atomic radius decreases across a period.
5. Therefore, the trend in atomic radius from left to right across a period is a decrease in atomic size.