Question

Assertion: The atomic radius decreases as we move from left to right in a period.

Reason: Effective nuclear charge increases across the period from left to right.

• A. Both assertion and reason are true and the reason is the correct explanation for the assertion.
• B. Both assertion and reason are true but the reason is not the correct explanation for the assertion.
• C. The assertion is true but the reason is false.
• D. The assertion is false but the reason is true.

Answer 1

The correct option is A Both assertion and reason are true and the reason is the correct explanation for the assertion.

In a period the number of shells or orbits is the same for every element in the period. The elements are arranged in increasing order of atomic number which means as we go from left to right in a period, the number of shells remains the same but the nuclear charge increases. The increased nuclear charge decreases the size of the atoms as it pulls the electrons in the last shell towards itself. So the size decreases as we move from left to right.