Pi and Sigma Bonds A sigma bond is either a single bond, or the first, and straight-line, bond of a double or triple bond. See page 246 for the actual appearance of a sigma and pi bond. A quick way to analyze pi and sigma bonds is that a single bond has 1 sigma, a double bond has 1 sigma and 1 pi, and a triple bond has 1 sigma and 2 pi.

Bond Strength and Length *Single bonds are longer than double bonds. *Triple bonds are the shortest *Triple bonds are much stronger than double bonds…double bonds are stronger than single bonds. *We can add up all of the bond energies of a compound and calculate the total energy stored in that compound. *An endothermic reaction absorbs energy. *An exothermic reaction releases energy.

8-2 Naming Molecular Compounds Molecular compounds are generally composed of 2 non-metals. Since there are multiple ways that non-metals can occur together, we need to use prefixes to tell how many of each atom are present. 1-mono 2-di 3-tri 4-tetra 5-penta 6-hexa 7-hepta 8-octa 9-nona 10-deca CO would be carbon monoxide CO2 would be carbon dioxide… mono can be skipped on the first element only.

Naming Acids You have an acid when the compound is in the form HX- where X- is any anion. HX 3 rules for naming acids… If there is 1 capital letter with H then rule 1.. 1. hydro_____ic acid (also any x- ending in ide.) If there are 2 or 3 capital letters with H then rule 2 or 3.. 2. ________ ous acid (also any x- ending in ite.) 3. ________ ic acid (also any x- ending in ate.)

See Examples:

Other polyatomic ions gain electrons to fill their shell also.