Question

Which of the following factors determines the trend of the atomic radius across a period?

[1 mark]

• A. Increase in atomic mass
• B. Decrease in atomic number
• C. Increase in effective nuclear charge
• D. Decrease in effective nuclear charge

Answer 1

The correct option is C Increase in effective nuclear charge

Atomic radius is the distance between the centre of the nucleus of an atom and its outermost shell. It is independent of atomic mass.

On moving from left to right across a period, the atomic size decreases due to an increase in the effective nuclear charge. As a result, the outermost electrons are attracted towards the nucleus with a greater force, thereby decreasing the atomic radius of the atom.