A molecular orbital (MO) diagram is a simple picture that shows how atomic orbitals combine to make molecular orbitals when atoms form a molecule.
Key points:
- Bonding orbitals (σ, π) → lower energy → make molecule stable.
- Antibonding orbitals (σ, π)** → higher energy → weaken molecule.
- Electrons fill orbitals from low to high energy.
- Bond order = (electrons in bonding − electrons in antibonding) ÷ 2 → tells if molecule is stable.
Example: H₂
- Each H atom has 1 electron → combine 1s orbitals → σ(1s) and σ*(1s).
- Both electrons go to σ(1s) → bond order = 1 → H₂ is stable.
In short:
It shows where electrons go in a molecule and explains bond strength and stability.