Hybridization of Atomic Orbitals

What is Hybridization?

• Definition: Combining atomic orbitals to form hybrid orbitals.
• Examples:
  • sp3 Hybrid Orbital: Combination of 1 s orbital and 3 p orbitals (1s + 3p).
  • sp2 Hybrid Orbital: Combination of 1 s orbital and 2 p orbitals (1s + 2p).
  • sp Hybrid Orbital: Combination of 1 s orbital and 1 p orbital (1s + 1p).
  • d2sp3 Hybrid Orbital: Combination of 2 d orbitals, 1 s orbital, and 3 p orbitals (2d + 1s + 3p).

Understanding Atomic Orbitals

• s Orbital: Spherical shape; represents the probability of finding an electron.
• p Orbitals: There are three types (p_x, p_y, p_z) oriented along the x, y, and z axes respectively.

Hybridization of Carbon

• Electron Configuration: 1s² 2s² 2p²
• Valence Electrons: Carbon has 4 valence electrons.

sp3 Hybridization

• Composition: 1 s orbital and 3 p orbitals.
• Character: 25% s character and 75% p character.
• Energy Level: Closer to 2p than to 2s.
• Degenerate Orbitals: All four sp3 hybrid orbitals have the same energy; electrons are placed one at a time with parallel spins.

sp2 Hybridization

• Composition: 1 s orbital and 2 p orbitals (one p orbital remains unhybridized).
• Character: 33% s character and 67% p character.
• Energy Level: Closer to 2p than to 2s, less than sp3.
• Hybrid Orbitals: Three sp2 hybrid orbitals formed, each containing one electron.

sp Hybridization

• Composition: 1 s orbital and 1 p orbital (two p orbitals remain unhybridized).
• Character: 50% s character and 50% p character.
• Energy Level: Located between the s and p orbitals.
• Hybrid Orbitals: Two sp hybrid orbitals formed.

Bonds in Hybridization

• Sigma Bonds: Formed from hybrid orbitals; every bond contains one sigma bond.
• Pi Bonds: Formed from unhybridized p orbitals; double bonds contain 1 pi bond, and triple bonds contain 2 pi bonds.
• Bond Strength:
  • Triple bonds are stronger than single bonds (3 bonds vs. 1 bond).
  • Sigma bonds are stronger than pi bonds (easier to break pi bonds).

Counting Sigma and Pi Bonds

• General Rule: Every bond consists of one sigma bond.
• Example: In a given structure:
  • Count sigma bonds: Total number of bonds.
  • Count pi bonds: Each double bond contributes one pi bond.
• Summary: If there are 7 sigma bonds and 2 pi bonds, the total is 7 sigma and 2 pi.