ICSE Class 10 Chemistry
Question 9 of 25
Periodic Table, Periodic Properties and Variations of Properties — Question 21
Back to all questions 21
Question Assertion (A): Atomic size increases along a period.
Reason (R): Effective nuclear charge increases with atomic number.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true but R is not the correct explanation of A.
- A is true but R is false.
- A is false but R is true.
A is false but R is true.
Explanation — Atomic size decreases across a period (from left to right) in the periodic table. This is because, although electrons are being added, they are added to the same shell, and the increasing effective nuclear charge pulls the electrons closer to the nucleus. Hence, Assertion (A) is false.
As atomic number increases, the number of protons increases, which increases the effective nuclear charge. Hence, Reason (R) is true.