VSEPR Theory

(noun)

the Valence Shell Electron Pair Repulsion (VSEPR) model is used to predict the shape of individual molecules based on the extent of electron-pair electrostatic repulsion

(noun)

a chemistry model used to predict the shape of individual molecules based on electron-pair electrostatic repulsion

Examples of VSEPR Theory in the following topics:

  • Table of Geometries

    • The VSPER theory detremines molecular geometries (linear, trigonal, trigonal bipyramidal, tetrahedral, and octahedral).
    • Molecular geometries (linear, trigonal, tetrahedral, trigonal bipyramidal, and octahedral) are determined by the VSEPR theory.
    • A table of geometries using the VSEPR theory can facilitate drawing and understanding molecules.
    • The bonded angles in the table are ideal angles from the simple VSEPR theory; the actual angle for the example given is in the following column.
    • Apply the VSEPR model to determine the geometry of a molecule that contains no lone pairs of electrons on the central atom.

  • Molecular Geometries

    • The VSEPR theory describes five main shapes of simple molecules: linear, trigonal planar, tetrahedral, trigonal bipyramidal, and octahedral.
    • VSEPR uses the steric number and distribution of X's and E's to predict molecular geometric shapes.
    • Examples of triatomic molecules for which VSEPR theory predicts a linear shape include BeCl2 (which does not possess enough electrons to conform to the octet rule) and CO2.
    • When writing out the electron dot formula for carbon dioxide, notice that the C-O bonds are double bonds; this makes no difference to VSEPR theory.
    • In accordance with the VSEPR theory, the bond angles between the electron bonds are 109.5o.

  • Applying the VSEPR Model

    • In the VSEPR model, the number of electron pairs around a central atom dictates a molecule's general shape.
    • The valence shell electron pair repulsion (VSEPR) model predicts the shape of individual molecules based on the extent of electron-pair electrostatic repulsion.
    • According to VSEPR, the valence electron pairs surrounding an atom mutually repel each other; they adopt an arrangement that minimizes this repulsion, thus determining the molecular geometry.
    • This makes no difference to VSEPR theory; the central carbon atom is still joined to two other atoms, and the electron clouds that connect the two oxygen atoms are 180° apart.
    • Lots and lots of practice problems for VSEPR theory.

  • Percent Ionic Character and Bond Angle

    • The more covalent in nature the bond, the more likely the atoms will situate themselves along the predetermined vectors given by the orbitals that are involved in bonding (VSEPR theory).

  • The Shape of Molecules

    • Bonding configurations are readily predicted by valence-shell electron-pair repulsion theory, commonly referred to as VSEPR in most introductory chemistry texts.
    • Nice treatments of VSEPR theory have been provided by Oxford and Purdue.
    • The following links will take you to Oxford's site (http://www.chem.ox.ac.uk/vrchemistry/vsepr/intro/vsepr_splash.html) and Purdue's site (http://www.chem.purdue.edu/gchelp/vsepr/).

  • Atomic and Molecular Orbitals

    • Thus, the four covalent bonds of methane consist of shared electron pairs with four hydrogen atoms in a tetrahedral configuration, as predicted by VSEPR theory.
    • These are useful models for explaining the structure and reactivity of many organic compounds, but modern molecular orbital theory involves the creation of an orbital correlation diagram.

  • Conflict Theory

    • Provide an overview of conflict theory, including its most prominent theorists.

  • Drive-Reduction Theory

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  • Drive Theory