MO diagrams of H₂, He₂, N₂, O₂, F₂, NO, CO — bond order, magnetism

2.3.13 · Chemistry › Chemical Bonding

MOs ki zaroorat kyun hai?

MO kya hai: ek molecule-wide electron wavefunction jo atomic wavefunctions ko combine karke banti hai — yani Linear Combination of Atomic Orbitals (LCAO).

Do AOs se do MOs kyun: waves do tarah se add ho sakti hain — in phase (constructive → electron density nuclei ke beech mein ikatti hoti hai → stabilizing) ya out of phase (destructive → nuclei ke beech ek node → destabilizing). Do inputs se do combinations milte hain.

${\psi }_{\text{bonding}}={\psi }_A+{\psi }_B{\psi }_{\text{antibonding}}={\psi }_A-{\psi }_B$

Koi bhi 2nd-period diagram kaise banayein

AOs $1s,2s,2p$ se MOs ka order:

B₂, C₂, N₂ ke liye (Z ≤ 7) — s–p mixing σ2p ko π2p ke upar dhakelta hai: ${\sigma }_{1s}<{\sigma }_{1s}^{\ast }<{\sigma }_{2s}<{\sigma }_{2s}^{\ast }<{\pi }_{2p_x}={\pi }_{2p_y}<{\sigma }_{2p_z}<{\pi }_{2p_x}^{\ast }={\pi }_{2p_y}^{\ast }<{\sigma }_{2p_z}^{\ast }$

O₂, F₂ ke liye (Z ≥ 8) — koi significant mixing nahi, σ2p π2p ke neeche: $\cdots <{\sigma }_{2p_z}<{\pi }_{2p_x}={\pi }_{2p_y}<{\pi }_{2p_x}^{\ast }={\pi }_{2p_y}^{\ast }<{\sigma }_{2p_z}^{\ast }$

Worked cases (MOs bharo, count karo, magnetism decide karo)

Flashcards

Connections

• Molecular Orbital Theory (LCAO basics)
• Hund's Rule and Pauli Exclusion
• Valence Bond Theory vs MO Theory
• Paramagnetism and Diamagnetism
• Bond Order, Bond Length, Bond Energy correlation
• Isoelectronic species (CO, N₂, CN⁻, NO⁺)
• s–p mixing and orbital energy ordering

Concept Map