Chapter 8: Section 3 Bonding Theories Covalent Bond­ Sharing electrons by overlapping of the outer level orbitals H Atom Orbital­ space occupied by 2 electrons in an ATOM H2 Molecule H Atom H Atom F Atom F Atom F2 Molecule Sigma Bonds 1 Bonds: When two atoms share 2 electrons, the result is a single bond. H­H Cl­Cl H­O­H Sigma bonds σ All single bonds are sigma bonds Made by: an s orbital overlapping another s orbital s­p overlap p­p end­to­end overlap 2 When two atoms share 4 electrons, the result is a double bond. O2 CO2 When two atoms share 6 electrons, the result is a triple bond. N2 Pi bonds π: Found in multiple bonds p­p parallel overlap Double bond = 1 σ and 1 π Triple bond = 1 σ and 2 π C2H2 3 Pi Bond C Atom C Atom C=C Pi Bond Double Bond= 1σ and 1π Sigma Bond Triple Bond 1σ & 2π 4 Single bond- 1 sigma One shared pair of electrons Double bond-1 sigma and 1 pi Two shared pairs of electrons Triple bond- 1 sigma and 2 pi Three shared pairs of electrons http://www.mhhe.com/physsci/chemistry/animations/chang_7e_esp/bom5s2_6.swf 5 VSEPR: Valence Shell Electron Pair Repulsion Model used to predict the shape of a molecule, based on the repulsion of shared and unshared pairs of electrons around the central atom of a molecule. Molecular orbitals Shared pair­ Two electrons shared between nuclei of 2 atoms Unshared pair­ Two electrons held by nucleus of only 1 atom This is a larger electron density area, has more repulsive power 6 OK...so I'm sure you've wondering HOW carbon can make FOUR bonds and sulfur can make SIX??? And the Noble gases???? 7 Hybridization Allows for more bond sites to form. Orbitals from different sublevels combine and share electrons to create more bond sites. C 1s22s22p2 2s 2p 2 3 Hybridized C 1s 2sp 4 orbitals available 3 2sp for bonding Can Nitrogen hybridize? Oxygen? 1s22s22p3 1s22s22p4 N=O=N??? Only elements in the 3rd period, and beyond; the ones that have a d sublevel available can hybridize. Carbon 8 Examples: What are the shapes, bond angles, and hybridizations of the following molecules? Use the flow chart and instructions above to figure it out. 1) carbon tetrabromide 2) phosphorus trichloride 3) oxygen 4) the chlorine atom in hydrochloric acid (HCl) 5) boron trichloride 6) CH2O 7) sulfur difluoride 8) either carbon atom in C2H2 9.