<p>08945f59de8843b7af64af74e4c99e28.doc SCH4U – Structure and Properties of Matter</p><p>Date: ______Valence Bond Theory</p><p>Developed by chemists Walter Heitler and Fritz London in 1927 Proposed that a ______forms when ______from two atoms ______</p><p>The two overlapping orbitals form one “______” which is a volume of space between two atomic nuclei in which there is a high probability of finding the now ______</p><p>Consider the electron orbital notation for Fluorine There is one empty space in the p-orbitals</p><p>Page 1 of 4 08945f59de8843b7af64af74e4c99e28.doc SCH4U – Structure and Properties of Matter</p><p>If two fluorine combine, they can share the single electrons</p><p>Let’s look at water (H2O)</p><p>A good bonding theory will explain all of the properties of the molecule’s structure including: ______, bond energy, ______and ______</p><p>Problem: for most molecules, the Valence Bond theory does not match ______observations Consider Water</p><p>The bonds in H2O would involve the oxygen “_____” orbitals overlapping with the hydrogen “_____” orbital As a result, an expected bond angle of ______Experimental observations show that the bond angle in water is ______</p><p>Page 2 of 4 08945f59de8843b7af64af74e4c99e28.doc SCH4U – Structure and Properties of Matter</p><p>Consider methane (CH4) The carbon atom would be using “_____” and “_____” orbitals to form bonds The energy of “_____” orbital electrons is higher than the energy of “____” orbital electrons, this should be reflected in the bond energies In the real molecule all bond energies are ______Also, this combination of orbitals can’t explain the tetrahedral shape of this molecule with bond angles of ______</p><p>Orbital Hybridization Theory Linus Pauling proposed: when bonding, the “______” atomic orbitals of the central atom are replaced with new “______” “s orbital” and “p orbitals” are reconfigured into “______hybrid orbitals” hybridizing electrons from one “____” orbital and three “____” orbitals results in four identical hybrid orbitals called “______hybrid orbitals” that are arranged in a tetrahedral pattern around the nucleus hybrid orbitals are ______in energy to the original “pure” orbitals</p><p>Page 3 of 4 08945f59de8843b7af64af74e4c99e28.doc SCH4U – Structure and Properties of Matter</p><p>Sigma Bonds (σ) A sigma bond is formed when two orbitals overlap in a direct “______” fashion The “______” formed by this type of overlap lies directly between and in the same plane as the two atomic ______This very effective overlap results in a very ______Pi Bonds (π) A pi bond is formed by the less effective “______” overlap of two “____” orbitals This results in the bonding orbital forming above and below the plane of the ______This less effective orbital overlap results in the pi bond being ______than the sigma bond</p><p>Page 4 of 4</p>