VSEPR Table: Predicting Molecular Geometry The Valence Shell Electron Pair Repulsion (VSEPR) theory is a fundamental model in chemistry used to predict the three-dimensional shapes of molecules. Based on the principle that electron pairs surrounding a central atom repel each other, VSEPR theory determines molecular geometry by minimizing this repulsion. A VSEPR Table is an essential tool for visualizing how the number of electron domains (bonding pairs and lone pairs) determines the shape and bond angles of a molecule. How to Use a VSEPR Table
To determine molecular shape using a VSEPR table, follow these steps:
Identify the central atom: Locate the central atom in the molecule.
Count valence electrons: Determine the number of valence electrons on the central atom.
Count bonding atoms: Add one electron for each atom bonded to the central atom.
Adjust for charge: Subtract an electron for a positive charge; add an electron for a negative charge.
Calculate electron pairs: Divide the total count by 2 to get the total number of electron pairs (domains). Comprehensive VSEPR Summary Table
The table below summarizes the relationship between electron domains, molecular geometry, hybridization, and bond angles. Electron Domains Bonding Pairs Lone Pairs Electron Geometry Molecular Shape Approx. Bond Angles 2 180∘180 raised to the composed with power BeCl2cap B e cap C l sub 2 CO2cap C cap O sub 2 3 Trigonal Planar Trigonal Planar 120∘120 raised to the composed with power BF3cap B cap F sub 3 NO3−cap N cap O sub 3 raised to the negative power 3 Trigonal Planar <120∘is less than 120 raised to the composed with power SO2cap S cap O sub 2 O3cap O sub 3 4 Tetrahedral Tetrahedral 109.5∘109.5 raised to the composed with power CH4cap C cap H sub 4 SiCl4cap S i cap C l sub 4 4 Tetrahedral Trigonal Pyramidal
<109.5∘is less than 109.5 raised to the composed with power NH3cap N cap H sub 3 PF3cap P cap F sub 3 4 Tetrahedral
≪109.5∘is much less than 109.5 raised to the composed with power H2Ocap H sub 2 cap O SCl2cap S cap C l sub 2 5 Trigonal Bipyramidal Trigonal Bipyramidal PF5cap P cap F sub 5 PCl5cap P cap C l sub 5 5 Trigonal Bipyramidal SF4cap S cap F sub 4 XeO2F2cap X e cap O sub 2 cap F sub 2 5 Trigonal Bipyramidal <90∘is less than 90 raised to the composed with power ClF3cap C l cap F sub 3 BrF3cap B r cap F sub 3 5 Trigonal Bipyramidal 180∘180 raised to the composed with power XeF2cap X e cap F sub 2 I3−cap I sub 3 raised to the negative power 6 Octahedral Octahedral SF6cap S cap F sub 6 PF6−cap P cap F sub 6 raised to the negative power 6 Octahedral Square Pyramidal <90∘is less than 90 raised to the composed with power BrF5cap B r cap F sub 5 XeOF4cap X e cap O cap F sub 4 6 Octahedral Square Planar 90∘90 raised to the composed with power XeF4cap X e cap F sub 4 ICl4−cap I cap C l sub 4 raised to the negative power Key Takeaways
Electron Repulsion: Lone pairs occupy more space than bonding pairs, leading to reduced bond angles in molecules like H2Ocap H sub 2 cap O NH3cap N cap H sub 3
Hybridization: The VSEPR table often includes hybrid orbitals, which correlate directly with the number of electron domains.
Multiple Central Atoms: Molecules with multiple central atoms are analyzed by determining the geometry around each individual atom.
For more detailed technical data and to find specific substances, check the SigmaAldrich VSEPR Chart article. VSEPR Chart | Valence Shell Electron Pair Repulsion Theory