Question

The conditions for the combination of atomic orbitals to form molecular orbitals are stated below. Mark the incorrect condition mentioned here.

• A. The combining atomic orbitals must have nearly same energy.
• B. The combining atomic orbitals must overlap to maximum extent.
• C. Combining atomic orbitals must have same symmetry about the molecular axis.
• D. Pi ($\pi$) molecular orbitals are symmetrical around the bond axis.

Answer 1

Answer: (D)

Pi ($\pi$) molecular orbitals are symmetrical around the bond axis.

$\pi -\pi molecularorbital$= The bonding electron density lies above and below, or in front and in back of the bonding axis, with no electron directly on the bonding axis, since $2p$ orbitals do not have any electron density at the nucleus,

$\sigma -\sigma molecularorbital$=Shared electron density is directly between the bonding atoms, along with the bonding axis. Electrons usually occupy these orbitals. A $sigma$ bond is always the first bond formed between two atoms.

So the correct option is [D].