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 3 4 2 2 3 1 shape Bent Trigonal pyramidal Example Linear ( ⁰ angle) Number of atoms bonded to central atom Number of unshared pairs of electrons Example Linear ( ⁰ angle) Trigonal planar Tetrahedral ( ⁰ angle) Bent Trigonal pyramidal 2 180 3 120 4 109.5 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 Must contain at least one polar bond 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