How does atomic radius change as you move from left to right across a period in the periodic table?

• A. It increases because electrons are added to higher energy levels.
• B. It increases due to the addition of more electron shells.
• C. It remains constant because the number of protons and electrons increases equally.
• D. It decreases due to increasing nuclear charge.

Answer: (D)

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. Recognize that as you move from left to right across a period in the periodic table, electrons are added to the same principal energy level (same shell), not to higher energy levels.
3. Note that protons are also added to the nucleus as you move across a period, increasing the nuclear charge (positive charge of the nucleus).
4. Because the added electrons are in the same shell, the increased nuclear charge pulls the electron cloud closer to the nucleus, reducing the atomic radius.
5. Therefore, the atomic radius decreases across a period due to the increasing nuclear charge attracting electrons more strongly, despite the addition of electrons.