Chemistry Chapter 9 Notes #4

Chapter 9 – Quick Review Covalent Bonds –Sharing of electrons Naming Molecules Writing Formulas Naming Acids/Writing Formulas Molecular Geometry Hybridization Polarity Types of intermolecular forces

Hybridization A process where atomic orbitals are mixed to form new identical “hybrid” orbitals Example = Carbon Carbon’s outer energy level =2 The s sublevel is full and the p sublevel has 2

Hybridization If carbon undergoes hybridization the 4 e- in energy level 2 all go to separate orbitals Carbon now has 4 e- that are ready to make bonds. 1s orbital and 3 p orbitals. Name= sp 3

Polarity Electron Affinity –measure of the tendency of an atom to accept an e- –Increases as you move to the right and up on the periodic table… Electronegativity –Ability of an atom to attract e- in a chemical bond –Increases as you move to the right and up on the periodic table…

Polarity Nonpolar covalent bonds –When 2 atoms bond and the difference in their electronegativity values are zero –Equal sharing of electrons between 2 atoms –Most commonly occurs in 2 identical atoms bonding together Ex. O 2, H 2, N 2, F 2, Cl 2, etc. Each of these is called a diatomic molecule Add to cheat sheet (halogens, O, H, N)

Polarity Polar Covalent Bonds –Unequal sharing of electrons –One electron is winning the tug of war over the shared electrons It is winning because it has a much stronger electronegativity If the difference in e- is greater than 0.4 = polar –Ex. H-Cl

Polarity

The polarity of each bond is decided by subtracting the electronegativities of each atom involved in the bond The polarity of a molecule is based on shape –Symmetric shapes = nonpolar –Asymmetric shapes = polar

Intermolecular Forces 1.Dispersion Forces –Occurs between nonpolar substances –Attraction between molecules is weak 2. Dipole-Dipole Forces –Occurs between polar substances –Stronger than dispersion 3. Hydrogen Bond –Especially strong attraction between H and F, O, or N