Molecular geometry valence-shell electron pair repulsion theory

Due to the simplicity and the ability to explain the spectroscopic and excited state properties, the MO theory in addition to easy adaptability for modern computers has gained tremendous popularity among chemists. The concept of directed valence, based on the principle of maximum overlap and valence shell electron pair repulsion theory (VSEPR), has successfully explained the molecular geometries and bonding in polyatomic molecules. 

VSEPR theory The VSEPR (valence shell electron-pair repulsion) theory says that the electron pairs around a central atom will try to get as far as possible from each other in order to minimize the repulsive forces. This theory is used to predict molecular geometry. 

Valence shell electron pair repulsion theory places the two electron pairs on Be 180° apart, that is, with linear electronic geometry. Both electron pairs are bonding pairs, so VSEPR also predicts a linear atomic arrangement, or linear molecular geometry, for BeCl2. 

The VSEPR (Valence Shell Electron-Pair Repulsion) theory allows chemists to predict the molecular geometry of molecules. The VSEPR theory assumes that the electron pairs around an atom, whether they re bonding (shared between two atoms) or nonbonding (not shared), will try to get as far apart from each other in space to minimize the repulsion between themselves. It s like going to a fancy party and seeing someone else wearing the exact same outfit. You re gonna try to stay as far away from that person as possible ... 

Molecular geometry Tetrahedron tetrahedral Trigonal (triangular) planar Valence shell electron-pair repulsion theory (VSEPR) Section 13.3 Angular Bent... 

Questions 19 through 30 For each molecule or ion, or for the atom specified in a molecule or ion, write the Lewis diagram, then describe (a) the electron-pair geometry and (b) the molecular geometry predicted by the valence shell electron-pair repulsion theory. Also sketch the three-dimensional ball-and-stick representation of each molecule or ion in Questions 19-22. 

The other approach to molecular geometry is the valence shell electron-pair repulsion (VSEPR) theory. This theory holds that... 

The Laplacian of the electron density plays a dominant role throughout the theory.191 In addition, Bader has shown that the topology of the Laplacian recovers the Lewis model of the electron pair, a model that is not evident in the topology of the electron density itself. The Laplacian of the density thus provides a physical valence-shell electron pair repulsion (VSEPR) basis for the model of molecular geometry and for the prediction of the reaction sites and their relative alignment in acid-base reactions. This work is closely tied to earlier studies by Bader of the electron pair density, demonstrating that the spatial localization of electrons is a result of a corresponding localization of the Fermi correlation hole. 

This chapter reviews molecular geometry and the two main theories of bonding. The model used to determine molecular geometry is the VSEPR (Valence Shell Electron Pair Repulsion) model. There are two theories of bonding the valence bond theory, which is based on VSEPR theory, and molecular orbital theory. A much greater amount of the chapter is based on valence bond theory, which uses hybridized orbitals, since this is the primary model addressed on the AP test. 

A Preview of the Chapter 8-2 Valence Shell Electron Pair Repulsion (VSEPR) Theory 8-3 Polar Molecules The Influence of Molecular Geometry 8-4 Valence Bond (VB) Theory... 

Valence-bond theory, 32—34, 42, 46 Valence electrons, 10 and Lewis structures, 20 Valence-shell electron pair repulsion and molecular geometry, 26-29, 45 L-Valine, 1054, 1059... 

Merchant et al. (2012) investigated the impact of a 3D desktop virtual reality environment on the learning of the valence shell electron pair repulsion (VSEPR) theory in an introductory chemistry class. Their sample consisted of 204 undergraduates enrolled in a chemistry course at a university in the USA. They used 11 -multiple-choice questions to assess the students understanding of molecular angles, molecular geometry, and species identifications. They also constructed 15 items to measure the students self-efficacy for learning VSEPR theory. The students self-efficacy was found to positively relate to their scores on the multiple-choice test. 

Molecular geometry is the general shape of a molecule as determined by the relative positions of the various atomic nuclei. A number of physical properties such as melting point, boiling point, density and a number of chemical properties are based on the molecular geometry. A very useful model to predict the general shape of a molecule was developed by Gillespie and Nyholm in 1957. The theory called the Valence Shell Electron Pair Repulsion (VSEPR pronounced as vesper) theory is an... 

The valence-shell electron-pair repulsion (VSEPR) rule states that aU groups emanating from an atom—whether single, double, or triple bonds, or lone pairs— wiU be in spatial positions that are as far apart from one another as possible. The VSEPR method does not consider singly occupied orbitals to be groups (see below for the reason). VSEPR is purely a theory based upon the notion that the electrostatic repulsions between entities consisting of two or more electrons dictate molecular geometries. 

Molecular Shapes The shapes of molecules can be predicted by combining Lewis theory with valence shell electron pair repulsion (VSEPR) theory. In tiiis model, electron groups— lone pairs, single bonds, double bonds, and triple bonds—aroxmd the central atom repel one another and determine the geometry of the molecule. 

---