Determine the Bond Order of BN. 6. Is BN2+ paramagnetic or diamagnetic? 7. Does the bond between boron and oxygen in BO become stronger or weaker when it becomes BO? 8. Compare and contrast VBT verus MOT for B2 MOT Worksheet-Dr. Kim-Ver.
The Correct Answer and Explanation is:
Let’s address each question step-by-step, with correct answers followed by a detailed 300-word explanation.
1. Determine the Bond Order of BN.
Answer: Bond Order = 2
2. Is BN²⁺ paramagnetic or diamagnetic?
Answer: Diamagnetic
3. Does the bond between boron and oxygen in BO become stronger or weaker when it becomes BO⁺?
Answer: Stronger
4. Compare and contrast VBT versus MOT for B₂ (Boron molecule).
Answer:
- Valence Bond Theory (VBT): Predicts no bond in B₂.
- Molecular Orbital Theory (MOT): Predicts a bond order of 1 and paramagnetism due to unpaired electrons in π orbitals.
Detailed Explanation (300+ words):
To determine the bond order of BN (boron nitride), we use Molecular Orbital Theory (MOT). The total number of electrons in BN is 12 (B = 5, N = 7). Following the MOT for diatomic molecules with total electrons ≤ 14 (like N₂), the molecular orbital filling order is:
σ(1s)², σ*(1s)², σ(2s)², σ*(2s)², π(2p_x)² = π(2p_y)², σ(2p_z)².
Counting bonding (8) and antibonding (4) electrons:
Bond Order = (Bonding – Antibonding)/2 = (8 – 4)/2 = 2.
For BN²⁺, removing two electrons typically occurs from the highest-energy orbitals, likely the π(2p) or σ(2p_z). If both are removed from π(2p), we now have paired electrons only, making BN²⁺ diamagnetic (no unpaired electrons).
Next, the bond strength in BO vs BO⁺: BO has 11 electrons. BO⁺ has 10 electrons, meaning one electron is removed from an antibonding orbital. Fewer antibonding electrons lead to a higher bond order and a stronger bond in BO⁺ than in BO. Therefore, BO⁺ has a stronger bond.
Comparing Valence Bond Theory (VBT) and Molecular Orbital Theory (MOT) for B₂:
- VBT struggles with delocalized bonding and cannot explain the magnetic behavior of molecules like B₂. VBT incorrectly predicts no bond in B₂ since it assumes each boron atom lacks unpaired electrons to overlap effectively.
- MOT accurately predicts that B₂ has a bond order of 1 and is paramagnetic, due to two unpaired electrons in the degenerate π(2p) orbitals.
In conclusion, MOT provides better predictions for molecular properties such as bond order, magnetism, and stability, especially for homonuclear diatomics like B₂, BN, and BO.
