Chemistry Chapter 9 9.1/9.2 Notes Part 2

Review Covalent Bonds Sharing of valence electrons Still atoms are trying to meet the octet rule # of unpaired valence electrons decides how many bonds an atom can make Use electron dot structures to see how many unpaired electrons there are in an atom Bonds can be single, double, or triple

Single Bonds One shared pair of electrons Total of 2 e- in the bond Also called a “sigma” bond It just refers to the fact that there is a direct overlap between the outer energy levels of the atoms that are sharing e-

Multiple Bonds Double Bond Triple Bond 2 shared pair 4 e- total 1 sigma 1 pi Triple Bond 3 shared, 6 e- 2 Pi (parallel overlap) Double bond – Red in the center = sigma Green = Pi (above & below)

Strength of Bonds Bond Length Bond Dissociation Energy The closer the nuclei are, the stronger the bond More shared pair = closer the nuclei are Bond Dissociation Energy Amount of energy it takes to break a covalent bond As bond length decreases, the bond dissociation energy increases

Covalent Compounds Properties Nonconductors Low melting Low boiling point Mostly gas at room temp Solids are soft and brittle

Covalent Network Solids Graphite V. Diamond (allotropes) Covalent Network Solids Examples: diamond and Quartz Covalently bonded in a crystal lattice (like an ionic compound) - a continuously bonded structure Hard, rigid High melting and boiling points nonconductors

Lewis Structures Electron diagrams of multiple atoms to show how they are arranged in molecules Ex. H2 H2O Ammonia Methane O2 CO2