2Please answer the following on your own piece of paper Draw the Lewis structure for:CaI2OCl2Indicate whether the compounds in number 1 are ionic or covalent and describe what is happening with the electrons in the compounds (who is giving, who is taking and who is sharing).
3Bond Strength and Length Strength, in general:Triple bonds are stronger than double which are stronger than single.See Table 16.3 on page 448Usually listed in kJ/molExample C2H2Length, in general:Triple bonds are shorter than double which are shorter than single.
4ResonanceStructures which occur when two or more equally valid Lewis structures can be written for the same molecule, yet neither is correct.Example: O3 (ozone)Since both of these structures imply that one bond is shorter than the other, neither is correct. Actual evidence indicates that both bonds are the same length. Connecting both structures by a double-headed arrow implies that the actual structure is a kind of hybrid of the two possibilities.
5Polyatomic Ions Multiple atoms with a charge. Usually contain covalent bonds.Example: CN-Show brackets and charges to indicate change in electron number.
6Coordinate Covalent Bond When both electrons in bond pair come from one atom.Example:NH4+Most polyatomic cations and anions contain covalent and coordinate covalent bonds.Can be shown as an arrow in the structural formula pointing away from the atom where the electrons originated.
7Two types in molecules: (both are different from ferromagnetism) Magnetisms?Two types in molecules:Diamagnetic – all electrons are pairedslightly repelled by a magnetParamagnetic – one or more unpaired electronsattracted to a magnetMass will appear greater in a magnetic field(both are different from ferromagnetism)
8When the octet rule does not work. Molecules with odd # of electrons ExceptionsWhen the octet rule does not work.Molecules with odd # of electronsNO
9Some molecules complex with others to complete an octet BF3NH3
10Some have expanded octets When there are more than an octet and it is obvious, turn the dots on the central atom into bonds. Then place the lone pairs on the terminal atoms.PCl5 and SF6(expanded since after the 3rd energy level “d” is there)
11Overview of Exceptions Phosphorus can make 5 bondsSulfur can make 6 bondsBoron can make 3 bondsBeryllium can make 2 bonds
12Shape Theory Ways to explain the shape of molecules. Hybridization (Next week’s discussion)VSEPR Theory (Today and Monday)
13VSEPR Theory Stands for: Valence Shell Electron Pair Repulsion Theory Electron pairs repel each other, whether they are in chemical bonds (bonding pairs) or unshared (lone pairs).Electron pairs assume orientations about an atom to minimize repulsions
14Applying the VSEPR Theory Draw a possible Lewis structure of the molecule.Determine the number of bonding pairs and lone pairs on the central atom.Find shape on handout and establish the geometry of the molecule about the central atom.If there is more than one central atom shape is described about all of the central atoms.