Valence Shell Electron Pair Repulsion (VSEPR) Theory
- 1. National Institute Of Technology Puducherry Course Code: ED1101 Course Name: Atomic Structure and Bonding Topic:VSEPR Theory SUBMITTED BY: A. Krishyaa ED24B1023 B.Sc.B.Ed (ITEP)Chemistry Major SUBMITTED TO: MR. S. Detchanamurthy Faculty Of Chemistry Department Of Education
- 2. NITPY Chemistry seminar Topic : VSEPR THEORY NAME : KRISHYAA ROLL NO : ED24B1023 DEPARTMENT : B. SC - B. ED - 1 YEAR
- 3. 3 WHAT IS VSEPR THEORY ? The Valence Shell Electron Pair Repulsion Model is often abbreviated as VSEPR (pronounced “vesper”). It is basically a model to predict the geometry of molecules. Specifically, VSEPR models look at the bonding and molecular geometry of organic molecules and polyatomic ions. It is useful for nearly all compounds that have a central atom that is not a metal.
- 4. 4 WHAT IS VSEPR THEORY ? The Valence Shell Electron Pair Repulsion Model is often abbreviated as VSEPR (pronounced “vesper”). It is basically a model to predict the geometry of molecules. Specifically, VSEPR models look at the bonding and molecular geometry of organic molecules and polyatomic ions. It is useful for nearly all compounds that have a central atom that is not a metal.
- 5. IMPORTANCE OF VSEPR MODEL : ● Lewis structures only tell the number and types of bonds between atoms, as they are limited to two dimensions. The VSEPR model predicts the 3-D shape of molecules and ions but is ineffective in providing any specific information regarding the bond length or the bond itself. ● VSEPR models are based on the concept that electrons around a central atom will configure themselves to minimize repulsion, and that dictates the geometry of the molecule. ● It can predict the shape of nearly all compounds that have a central atom, as long as the central atom is not a metal. Each shape has a name and an idealized bond angle associated with it. 5
- 6. 6 COMMONLY USED MOLECULES SHAPES ● Bond Angle: This is the angle between a bonded atom, the central atom, and another bonded atom. ● Lone Pair: This refers to a pair of valence electrons that are not shared with another atom. ● Molecular Geometry: This is the 3-D arrangement of bonded atoms in a polyatomic ion or molecule. ● Electron Pair Geometry: This is the 3-D arrangement of electron pairs around the central atom of a polyatomic ion or molecule.
- 7. 7 LIMITATIONS OF VSEPR THEORY ● The VSEPR model is not a theory. It does not explain or attempt to explain any observations or predictions. Rather, it is an algorithm that accurately predicts the structures of a large number of compounds. ● VSEPR is simple and useful but does not work for all chemical species. ● First, the idealized bond angles do not always match the measured values. For example, VSEPR predicts that and will have the same bond angles, but structural studies have shown the bonds in the two molecules are different by 12 degrees. ● VSEPR also predicts that group-2 halides such as will be linear when they are actually bent. Quantum mechanics and atomic orbitals can give more sophisticated predictions when VSEPR is inadequate.
- 8. 8 VSEPR Number Shape of the molecule 2 Linear 3 Trigonal 4 Tetrahedral 5 Trigonal bipyramidal 6 Octahedral 7 Pentagonal bipyramidal
- 9. What are Amino Acids? Introduction to DNA 9 In summary, VSEPR Theory serves as a fundamental tool in molecular chemistry for predicting the shapes of molecules based on electron pair repulsion. Despite its limitations, it provides valuable insights into molecular behavior, aiding chemists in understanding chemical reactivity and properties Conclusion
- 10. QUESTIONS 1. Question: What is the main idea of VSEPR theory? Answer: VSEPR theory states that electron pairs in the valence shell of an atom repel each other and move as far apart as possible. 2. Question: What is the shape of a molecule with 4 bonding pairs and no lone pairs? Answer: Tetrahedral. 3. Question: What is the effect of lone pairs on the shape of a molecule? Answer: Lone pairs repel bonding pairs, causing the molecule to be more bent. 4. Question: What is the shape of a molecule with 3 bonding pairs and 1 lone pair? Answer: Trigonal pyramidal. 5. Question: What is the shape of a molecule with 2 bonding pairs and 2 lone pairs? Answer: Bent.
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