Sigma and Pi Bonds & Hybridization ✏ Chemistry In a Nutshell

Rucete ✏ Chemistry In a Nutshell 

 

1. Sigma (σ) and Pi (π) Bonds

Sigma (σ) Bonds

• Formed by direct orbital overlap between two atoms.
• Stronger than π bonds because of direct overlap.
• Types of Orbital Overlaps:
  • s-s overlap → (e.g., H₂)
  • s-p overlap → (e.g., HF)
  • p-p overlap → (e.g., F₂)
• All single bonds (σ bonds) are present in both single and multiple bonds.

Pi (π) Bonds

• Formed by side-by-side overlap of p orbitals.
• Weaker than σ bonds because of less effective overlap.
• Found in multiple bonds:
  • Double bonds = 1 σ + 1 π bond (e.g., C=C in ethene).
  • Triple bonds = 1 σ + 2 π bonds (e.g., C≡C in ethyne).
• π bonds add rigidity to molecules (e.g., restrict rotation in C=C).

2. Hybridization

• Hybridization occurs when atomic orbitals mix to form new orbitals that allow molecules to have specific geometries.

Types of Hybridization & Molecular Geometry

Hybridization	Molecular Geometry	Total Electron Pairs	Example
sp	Linear (180°)	2	BeCl₂, CO₂
sp²	Trigonal Planar (120°)	3	BF₃, SO₃
sp³	Tetrahedral (109.5°)	4	CH₄, NH₃
sp³d	Trigonal Bipyramidal (90°/120°)	5	PCl₅
sp³d²	Octahedral (90°)	6	SF₆

In a nutshell

1. Sigma (σ) bonds are stronger and found in all bonds.
2. Pi (π) bonds are weaker and found only in double and triple bonds.
3. Hybridization determines molecular geometry:
• sp → Linear (180°)
• sp² → Trigonal Planar (120°)
• sp³ → Tetrahedral (109.5°)
• sp³d → Trigonal Bipyramidal (90°, 120°)
• sp³d² → Octahedral (90°)

"Lions Try To Teach Tigers, Only Silly People Bite!"
(Linear, Trigonal Planar, Tetrahedral, Trigonal Bipyramidal, Octahedral)