Molecular Orbitals

When atomic orbitals interfere constructively with each other, they increase the chances of finding electrons between nuclei, forming what we call a bond.

Types of Bonds

  • A sigma (σ)-bond is formed by one region of constructive overlap between orbitals (regardless of the type of orbital used).
  • A pi (π)-bond is formed by two regions of constructive overlap between orbitals (p-orbitals).

The LCAO Model: Predicting Molecular Orbitals

The hexagon-thingy in the middle is the LCAO (Linear Combination of Atomic Orbitals):

  • The side orbitals are your atomic orbitals (like you are used to drawing)
  • The top and bottom orbitals represent atomic orbital overlap (molecular orbitals).
  •  When atomic orbitals constructively interfere, they create bonding molecular orbitals that are more stable than the original atomic orbitals.

Bond Lengths and Strengths

Concept: Sigma bond vs. pi bond, which is stronger? 


Hey! Turn that frown upside-down. I know this section blows. The rest of this chapter should be cake compared to this.