Chapter_10_Part_2 - Chapter 10: Molecular Geometry and...

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Unformatted text preview: Chapter 10: Molecular Geometry and Chemical Bonding Theory Part 2 d. Central Atom with Five or Six Valence–Shell Electron Pairs Electron Pair Arrangements Electron Pair Arrangement • five pairs of electrons (regions of electron density) • six pairs of electrons (regions of electron density) trigonal bipyramidal octahedral Molecular Geometry Molecular geometry • five pairs of electrons (regions of electron density) no lone pair of electrons one lone pair of electrons two lone pairs of electrons three lone pairs of electrons • six pairs of electrons (regions of electron density) no lone pair of electrons one lone pair of electrons two lone pair of electrons Chapter 11 trigonal bipyramidal seesaw T–shaped linear octahedral square pyramidal square planar Part 2 1 of 3 2. Dipole Moment and Molecular Geometry To understand dipole moment, we need to understand the concept of electronegativity. Electronegativity is a measure of the ability of an atom in a bond to draw bonding electrons to itself. Electronegativity increases from bottom to top in a group and from left to right across a period (excepting Group VIIIA). Any bond between two atoms with different electronegativies is a polar bond. That means that the bonding electrons pairs spend more time near the more polar atom than with the less polar atom. This can be described as one atom having a partial negative charge (d–) and a partially positive charge (d +). The greater the difference, the more polar the bond. Dipole moment is a quantitative measure of charge separation in a molecule. Molecules with some molecular geometries tend to have dipole moments. Molecules with one or more lone pair tend to have a dipole moment. Dipole moment can be measured are made based on the fact that polar molecules align in an electric field and have an impact on the capacitance of the charged plates. See the Figure at the right. Chapter 11 Part 2 2 of 3 Table 10.1 (below) correlates molecular geometry with dipole moment. Chapter 11 Part 2 3 of 3 ...
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This note was uploaded on 04/02/2008 for the course CHM 1220 taught by Professor Barber during the Fall '07 term at Wayne State University.

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