Question

Considering x-axis as the internuclear axis which out of the following will not form a sigma bond and why?

• A. 1s and 1s
• B. 1s and 2p_x
• C. 2p_y and 2p_y
• D. 1s and 2s

Answer 1

The Correct Option is C

The question asks which of the given options will not form a sigma (σ) bond when considering the x-axis as the internuclear axis. Let's analyze each option to determine the correct answer:

1. 1s and 1s:
   • The 1s atomic orbitals are spherical and can overlap head-on along the internuclear axis to form a sigma bond. Therefore, 1s and 1s can form a σ bond.
2. 1s and 2p_x:
   • The 1s orbital is spherical, and the 2p_x orbital is directional along the x-axis. They can overlap head-on to form a sigma bond. Therefore, 1s and 2p_x can form a σ bond.
3. 2p_y and 2p_y:
   • The 2p_y orbitals are oriented perpendicular to the x-axis. Since they do not overlap head-on along the x-axis (internuclear axis), they cannot form a sigma bond. Thus, 2p_y and 2p_y cannot form a σ bond.
4. 1s and 2s:
   • Both 1s and 2s orbitals are spherical, allowing them to overlap head-on along the internuclear axis to form a sigma bond. Therefore, 1s and 2s can form a σ bond.

Conclusion: Based on the above analysis, the pair 2p_{y} and 2p_{y} cannot form a sigma bond when the x-axis is considered as the internuclear axis because these orbitals are oriented in a direction perpendicular to the x-axis, preventing head-on overlap.