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 number of shells remains the same while the effective nuclear charge increases. This leads to the stronger pulling of electrons from the outermost shell towards the nucleus, therefore decreasing the atomic size.