Finishing off Hybridization SCH4U1 February 22nd 2011 Mr. Dvorsky

Sigma and Pi Bonds Partial hybridization of the available orbitals is possible –leaving one or two p orbitals with single unpaired electrons Let us again use carbon as an example: Instead of mixing all four orbitals, only three are mixed forming three sp2 hybrid orbitals and an unhybridized p orbital

Sigma and Pi Bonds In a molecule like C2H4, three hybrid orbitals are used to form single bonds between carbon and hydrogen atoms. These single bonds are called sigma bonds All atoms in a molecule are attached by a sigma bond

Sigma and Pi Bonds The half filled p orbital on each carbon overlaps to form a pi bond It is an area of electron density above and below the sigma bond. Creates greater force between the two carbon atoms. Double bonds are stronger than single bonds

SCH4U1 February 22nd 2011 Mr. Dvorsky VSEPR Theory SCH4U1 February 22nd 2011 Mr. Dvorsky

Shapes of Molecules Ionic bonding is nondirectional, which means that ions will attract others of opposite charge with the same force regardless of where these other ions are located around the ion in question. Covalent bonds are directional, which means for a given central atom there is a preferred orientation for the other atoms attached to it. Shapes of molecules are important, i.e. Enzymes in biochemical reactions

VSEPR Theory VSEPR -valence shell electron pair repulsion Because electrons repel, molecules adjust their shape so that valence electron pairs are as far apart as possible to minimize repulsion. Unshared electrons take up more room than the bonding electrons. In terms of decreasing repulsion: LP – LP > LP – BP > BP – BP

VSEPR Theory The process of predicting shape: Determine what the central atom is Draw the Lewis structure for the molecule Determine the # of bonding pairs and lone pairs around the central atom Refer to the chart and determine the shape of the molecule

VSEPR Theory Fill in chart

SCH4U1 February 22nd 2011 Mr. Dvorsky Electronegativity SCH4U1 February 22nd 2011 Mr. Dvorsky

Electronegativity