Molecular Structures :: essays research papers

Covalent Bonding and Molecular GeometryObjectiveThe objective of this exercise is to help in understanding the geometric relationships of atoms in simple molecules and the relationship of hybridization to the geometry present.DiscussionIn the last 30 years, data obtained from spectrometric measurements, X&64979ray and electron diffraction studies, and other experiments have yielded hairsplitting information about bond distances, tumbles, and energies. In many cases, the data confirmed conclusions reached earlier. In other cases, valuable new insights were acquired. Structure theory has advanced faraway beyond the simple electron dot representations and now rests securely on the foundations of quantum and wave mechanics. Although problems involving only simple molecules can now be solved with numeral rigor, approximations such as the valence bond theory and the molecular orbital theory are very successful in giving results that agree with observational measurements.This exercise will use valence bond theory or hybridization to look at the geometry formed from various hybridizations. You will use a framework model kit which gives the correct angles for the each of these hybridizations.The first bond formed between any two atoms is always a sigma (s)&64979bond (one that is isosceles about the bond axis). Additional bonds between the said(prenominal) two atoms will be pi (p)&64979bonds (perpendicular to the bond axis). It is the sigma&64979bonds and any lone&64979pairs of electrons occupying the sigma hybrid orbitals that determine the geometry of a molecule. Pi&64979bonds are always perpendicular to the sigma&64979bonds and follow the geometry formed by the sigma&64979bonding.ProcedureCheck out a molecular model kit from the stockroom. strike the kit directions to see which framework center is used for each hybridization.Tetrahedral (sp3 hybridization)CH4Construct a model of methane using a tetrahedral center (4 prongs) and four rods of the same glossary to show how the 4 Hs are attached.GeometryLewis dot diagram of s bonds on CApproximate H-C-H angelMax atoms (incl. C) in one planeIs in that respect a mirror plane(divides the molecule in equal halves) ?H3C&64979CH3 Construct a model of ethane using a tetrahedral center for each C and the same color rods for all 6 Hs with a C&64979C bond present.GeometryLewis dot diagram of s bonds on each CApproximate H-C-H angleApproximate H-C-H angleThe C-C bond is a single bond and has free rotation about it. Arrange the ethane molecule so that each C&64979H bond on one C atom is exactly parallel to a C&64979H bond on the second C atom. (This is the eclipsed position.) View this arrangement by looking along the C&64979C bond such that the atoms on the front C blank out those on the back C.