As you move from left to right across a period in the periodic table, what happens to the atomic radius of the elements?

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

Answer: (B)

Verified step by step guidance

1. Understand that the atomic radius is the average distance from the nucleus to the outermost electrons in an atom.
2. Recognize that as you move from left to right across a period in the periodic table, the number of protons in the nucleus increases, which means the nuclear charge increases.
3. Note that although electrons are added as you move across the 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 electrons closer to the nucleus without much additional shielding, the atomic radius decreases across the period.
5. Therefore, the trend is that the atomic radius decreases from left to right across a period in the periodic table.