Question

Group IA atoms are largest in their horizontal period, because of

• A. Highly effective nuclear charge
• B. Least effective nuclear charge
• C. No nuclear charge
• D. None of the above.

Answer 1

The correct option is B Least effective nuclear charge

The group IA atoms are largest in their horizontal period, because of lease effective nuclear charge(As the number of protons in the nucleus is less, the attractive force felt on the outer electrons is very low leading to least effective nuclear charge. As we go along the horizontal period the atomic no increase.The number of protons in the nucleus increases, which causes the increase in nuclear charge leading to smaller radii of the atom.