Question 3 - Assertion Reasoning questions (MCQ) - Chapter 5 Class 10 - Periodic Classification of Elements

Assertion (A): Be and Al show some similar properties.

Reason (R): The metallic radius of Be is less than the metallic radius of Al.

Answer

Be and Al are diagonally opposite each other in the modern periodic table and they have the same polarising power. Thus, they have similar properties.

Be has a metallic radius of 111 nm and Al has a metallic radius of 143 nm. So, Be is smaller than Al.

This small size of Be is the reason for its anomalous behavior (it has properties slightly different from other members of the same group) but not for its diagonal relationship with Al.

Thus,

• Assertion is true.
• Reasoning is true.
• The reasoning is not the correct explanation for assertion.

Therefore, the correct answer is (b) Both assertion and reason are correct but reason is not the correct explanation for assertion.