Given below are two statements : One is labelled as 

Assertion A and the other is labelled as Reason R

Assertion A: Zero orbital overlap is an out of phase overlap.

Reason : It results due to different orientation/direction of approach of orbitals.

In the light of the above statements. Choose the correct answer from the options given below

Zero orbital overlap is an out-of-phase overlap.

This is true because in out-of-phase overlap, the positive lobe of one orbital overlaps with the negative lobe of another orbital. Their electron densities cancel each other, so no effective overlap occurs → hence called zero overlap.

Reason (R):

It results due to different orientation/direction of approach of orbitals.

This is also true, because when orbitals approach each other in the wrong orientation (e.g., p_x trying to overlap with p_y), the wave functions do not match properly, leading to cancellation → zero overlap.

Correct Answer:

Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).