Chemistry - CHEMICAL BONDING Question with Solution | TestHub

The question asks which properties of N₂ do NOT change if sp intermixing and Hund's rule are ignored.

1. Bond Order: Bond order is calculated as $\frac{1}{2}$ (number of electrons in bonding orbitals - number of electrons in antibonding orbitals). For N₂, the total number of valence electrons is 10. The filling of molecular orbitals (MOs) for N₂ is $({\sigma }_{2s}{)}^2({\sigma }_{2s}^{\ast }{)}^2({\pi }_{2p}{)}^4({\sigma }_{2p}{)}^2$. This gives a bond order of $\frac{1}{2}(8-2)=3$. Even without sp intermixing, the number of bonding and antibonding electrons remains the same, so the bond order does not change.

2. Magnetic Behavior: N₂ is diamagnetic because all electrons are paired. This property is determined by the pairing of electrons, which is not affected by the presence or absence of sp intermixing or Hund's rule for N₂.

3. HOMO (Highest Occupied Molecular Orbital): With sp intermixing, the HOMO of N₂ is the ${\sigma }_{2p}$ orbital. Without sp intermixing, the order of MOs changes, and the ${\pi }_{2p}$ orbitals become higher in energy than the ${\sigma }_{2p}$ orbital. Thus, the HOMO changes from ${\sigma }_{2p}$ to ${\pi }_{2p}$.

4. LUMO (Lowest Unoccupied Molecular Orbital): With sp intermixing, the LUMO of N₂ is the ${\pi }_{2p}^{\ast }$ orbital. Without sp intermixing, the order of MOs changes, but the LUMO remains the ${\pi }_{2p}^{\ast }$ orbital.

Therefore, Bond order, Magnetic behavior, and LUMO do not change.

The final answer is $\boxed{A,B,D}$