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Real Molecule Shapes. Any molecule containing only 2 atoms has a linear shape. To predict shapes of molecules with more than 2 atoms we use VESPR theory VESPR stands for VALENCE SHELL ELECTRON PAIR REPLUSION
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Real Molecule Shapes • Any molecule containing only 2 atoms has a linear shape. • To predict shapes of molecules with more than 2 atoms we use VESPR theory • VESPR stands for VALENCE SHELL ELECTRON PAIR REPLUSION • Since electrons repel each other, electron pairs will be as far apart as possible. http://www.youtube.com/watch?v=keHS-CASZfc&feature=related Episode 503
2 0 180 3 0 120 4 0 109.5 2 2 3 1 Episode 503
More molecular shapes… Episode 503
What is the molecular geometry of C2H4? • Determine the shape each carbon atom • 2 trigonal planar connected with a double bond Episode 503
Polar Molecules http://education.jlab.org/frost/polar_molecules.html • Must contain at least one polar bond • Are shaped so that there is a (+) and a (-) end • Example of a polar molecule • H2O Episode 503
Non-Polar Molecules • Contain only non-polar bonds • Contain polar bonds, but has no charged ends • example of a non-polar molecule • CCl4 • C en.=2.5 • Cl en.= 3.5 3.5 -2.5 = 1.0 (polar bond) Episode 503
Intermolecular Forces • Force of attraction between molecules • Are weaker than covalent and ionic bonds • 3 types • Dipole to dipole • Force of attraction between the positive end of one molecule and negative end of a molecule • The stronger of all intermolecular forces • Hydrogen bonding (special type of dipole) • Occurs in molecules with H-F, H-O, and H-N bonds • Large positive charge of H is attracted to an unshared pair of electrons on a neighboring molecule • London Dispersion Forces • Weak intermolecular forces resulting from constant motion of electrons • The only type of intermolecular force between non-polar molecules (actual observed in all molecules) Episode 503