1. Guidelines for writing Lewis Dot Structures Identify the central atom (the atom to which the other atoms will be attached) -The central atom is the one having the lowest ionization energy (or lowest electronegativity) Determine the total number of valence electrons –Remember to include any extra electrons, if present

2. Guidelines for writing Lewis Dot Structures Arrange atoms in a symmetrical fashion (remember that this is being done in 2 dimensions rather than 3) Use a single pair of electrons for each bond Place remaining electrons around the rest of the atoms in groups of 2

3. Guidelines for writing Lewis Dot Structures Use the OCTET RULE to determine the exact arrangement of electrons with each atom The only exception to the octet rule is hydrogen which requires only 2 electrons.

4. Guidelines for writing Lewis Dot Structures Sharing of a single pair of electrons between two atoms constitutes a single bond which is called a sigma bond (  ) The electrons in a bond are counted twice, once with each of the atoms that form the bond to determine if the octet rule is satisified

5. Guidelines for writing Lewis Dot Structures Sharing of two or more pairs of electrons between 2 atoms constitutes a multiple bond - The first pair of electrons is a sigma bond (  ) - each of the remaining pairs of electrons forms a bond which is called a pi bond (  )

12. Resonance

13. A sigma (  ) bond centers along the internuclear axis. A pi (  ) bond occupies the space above and below the internuclear axis. Sigma and Pi Bonds

14. Summary of Bonding Types # of  bonds # of  bonds (Honors) Steric Number # of pairs of non-bonded electrons VSEPR designation Bond angle,  Molecular Geometry 4040 sp 3 109.5 Tetrahedral 3041 sp 3 107.5Trigonal Pyramidal 2042 sp 3 104.5Bent 3130 sp 2 120Trigonal Planar 2220 sp 180Linear