Ch.10 - Molecular Shapes & Valence Bond TheorySee all chapters
All Chapters
Ch.1 - Intro to General Chemistry
Ch.2 - Atoms & Elements
Ch.3 - Chemical Reactions
BONUS: Lab Techniques and Procedures
BONUS: Mathematical Operations and Functions
Ch.4 - Chemical Quantities & Aqueous Reactions
Ch.5 - Gases
Ch.6 - Thermochemistry
Ch.7 - Quantum Mechanics
Ch.8 - Periodic Properties of the Elements
Ch.9 - Bonding & Molecular Structure
Ch.10 - Molecular Shapes & Valence Bond Theory
Ch.11 - Liquids, Solids & Intermolecular Forces
Ch.12 - Solutions
Ch.13 - Chemical Kinetics
Ch.14 - Chemical Equilibrium
Ch.15 - Acid and Base Equilibrium
Ch.16 - Aqueous Equilibrium
Ch. 17 - Chemical Thermodynamics
Ch.18 - Electrochemistry
Ch.19 - Nuclear Chemistry
Ch.20 - Organic Chemistry
Ch.22 - Chemistry of the Nonmetals
Ch.23 - Transition Metals and Coordination Compounds
Jules Bruno

Valence shell electron pair repulsion (VSEPR) theory is a model for predicting the overall shape of a molecule. Molecular geometry represents the accurate three-dimensional shape of a compound that takes into account the effects of lone pairs, bond lengths, bond angles and the atomic size of elements. 


How to Determine Molecular Geometry

A domain represents the number of surrounding elements and lone pairs on the central element. Under molecular geometry we treat surrounding elements as different from the lone pairs on the central element. 

A = Central Element            X = Surrounding Element            E = Lone Pair (nonbonding electrons)

Domain of 2 

When a molecule has a domain of 2 then only AX2 is possible. An AX2 molecule would have a central element (A) connected to 2 surrounding elements (X) and possess a linear molecular geometry. 

CO2-HCN-Table-Chart-Electron-Groups-AXNAX2 - Linear (CO2 & HCN Domain of 2)

Domain of 3

A domain of 3 has AX3 and AX2E1 as possible orientations. For an AX3 orientation the central element (A) is connected to 3 surrounding elements (X) and possess a trigonal planar molecular geometry. 

BF3-Electron-Pair-Number-of-lone-pair-Trigonal-PlanarAX3 - Trigonal Planar (BF3 Domain of 3)

For an AX2E1 orientation the central element (A) is connected to 2 surrounding elements (X), 1 lone pair (E) and possess a bent molecular geometry. 

SnCl2-Bent-Angular-V-shapedAX2E1 - Bent, Angular or V-Shaped (SnCl2 Domain of 3)

Domain of 4

A domain of 4 has AX4, AX3Eand AX2E2 as possible orientations. For an AX4 orientation the central element (A) is connected to 4 surrounding elements (X) and possess a tetrahedral molecular geometry. 

CCl4-TetrahedralAX4 - Tetrahedral (CCl4 Domain of 4)

For an AX3E1 orientation the central element (A) is connected to 3 surrounding elements (X), 1 lone pair (E) and possess a trigonal pyramidal molecular geometry. 

NH3-Trigonal-PyramidalAX3E1 - Trigonal Pyramidal (NH3 Domain of 4)

For an AX2E2 orientation the central element (A) is connected to 2 surrounding elements (X), 2 lone pairs (E) and possess a bent molecular geometry. 

H2O-Bent-Domain-ChartAX2E2 - Bent, Angular, V-Shaped (H2O Domain of 4)

Domain of 5

A domain of 5 has AX5, AX4E1, AX3E2, and AX2E3 as possible orientations. For an AX5 orientation the central element (A) is connected to 5 surrounding elements (X) and possess a trigonal bipyramidal molecular geometry. 

PCl5-Trigonal-BipyramidalAX5 - Trigonal Bipyramidal (PCl5 Domain of 5)

For an AX4E1 orientation the central element (A) is connected to 4 surrounding elements (X), 1 lone pair (E) and possess a seesaw geometry. 

SF4-SeesawAX4E1 - Seesaw (SF4 Domain of 5)

For an AX3E2 orientation the central element (A) is connected to 3 surrounding elements (X), 2 lone pairs (E) and possess a T-shape geometry. 

ClF3-T-ShapedAX3E2 - T-Shaped (ClF3 Domain of 5)

For an AX2E3 orientation the central element (A) is connected to 2 surrounding elements (X), 3 lone pairs (E) and possess a linear geometry. 

XeF2-Linear-Domain-of-5AX2E3 - Linear (XeF2 Domain of 5)

Domain of 6

A domain of 6 has AX6, AX5E1, and AX4E2 as possible orientations. For an AX6 orientation the central element (A) is connected to 6 surrounding elements (X) and possess an octahedral molecular geometry. 

SCl6-OctahedralAX6 - Octahedral (SCl6 Domain of 6)

For an AX5E1 orientation the central element (A) is connected to 5 surrounding elements (X), 1 lone pair (E) and possess a square pyramidal geometry. 

SF5-Square-PyramidalAX5E1 - Square Pyramidal (SF5 Domain of 6)

For an AX4E2 orientation the central element (A) is connected to 4 surrounding elements (X), 2 lone pairs (E) and possess a square planar geometry. 

XeH4-Square-PlanarAX4E2- Square Planar (XeH4 Domain of 6)

Your understanding of these molecular geometries will be important in your understand of additional Lewis structure concepts such as the electron geometryhybridizationpolarity, the intermolecular forces and other essential bonding theories. 


Jules Bruno

Jules felt a void in his life after his English degree from Duke, so he started tutoring in 2007 and got a B.S. in Chemistry from FIU. He’s exceptionally skilled at making concepts dead simple and helping students in covalent bonds of knowledge.