Question

The atomic radius decreases as we move across a period because:

• A. atomic mass increases.
• B. atomic number increases.
• C. effective nuclear charge increases.
• D. more electrons are added.

Answer 1

The correct option is C

effective nuclear charge increases.

The distance between the center of the nucleus and the outermost shell of an atom is known as the atomic radius. Across a period the atomic size decreases as the number of shells remain the same but the electrons are been added so the nuclear charge increases. This leads to the stronger pulling of electrons from the outermost shell towards the nucleus thereby decreasing the size.