Question

Given below are two statements:
Statement (I): A \(\pi\) bonding MO has lower electron density above and below the inter-nuclear axis.
Statement (II): The \(\pi^*\) antibonding MO has a node between the nuclei.
In the light of the above statements, choose the most appropriate answer from the options given below:

• A. Both Statement I and Statement II are false
• B. Both Statement I and Statement II are true
• C. Statement I is false but Statement II is true
• D. Statement I is true but Statement II is false

Answer 1

The Correct Option is C

To evaluate the veracity of the provided statements regarding molecular orbitals, understanding \(\pi\) bonding molecular orbitals (MOs) and \(\pi^*\) antibonding molecular orbitals is essential.

1. Statement I: A \(\pi\) bonding MO exhibits reduced electron density above and below the inter-nuclear axis.
   • \(\pi\) bonding MOs are generated through the lateral overlap of p orbitals. In these MOs, electron density is concentrated in two lobes situated above and below the plane of the inter-nuclear axis, with minimal density on the axis itself. The assertion of "lower" electron density in these regions contradicts the nature of \(\pi\) bonding MOs, where electron density is maximized. Consequently, Statement I is invalidated.
2. Statement II: The \(\pi^*\) antibonding MO contains a node situated between the nuclei.
   • \(\pi^*\) antibonding MOs, also formed by the lateral overlap of p orbitals, do so in an out-of-phase manner. This arrangement creates a nodal plane between the nuclei, characterized by zero electron density, which is a defining feature of antibonding molecular orbitals. Therefore, Statement II is substantiated.

Based on the preceding analysis:

• Statement I is deemed false, as a \(\pi\) bonding MO is characterized by increased electron density above and below the inter-nuclear axis.
• Statement II is confirmed as true, accurately describing the \(\pi^*\) antibonding MO as possessing a node between the nuclei.

Therefore, the correct determination is: Statement I is false while Statement II is true.