UNIT VIII Lewis Structure Lesson 5

Lewis Structure

Gilbert Newton Lewis Invented “Electron-dot” formulas or “Lewis Structures” I’m so tired of writing all those useless inner electrons, in the Bohring models!

Valence Electrons – electrons in the outermost occupied energy level. (s and p electrons outside the core) Valence electrons can be represented by “dots” drawn around the atom.

Remember the rules…

VIII.3 CHEMICAL BONDING C. Writing Lewis Structures a. Simple Ionic Compounds: Draw the Lewis Structure of: a) MgO

VIII.3 CHEMICAL BONDING b)KCl c) CaF 2

VIII.3 CHEMICAL BONDING b. Covalent Compounds: Octet Rule : most atoms, other than hydrogen, tend to attain an octet of electrons as a result of forming covalent bonds

VIII.3 CHEMICAL BONDING Rules: 1. Count the TOTAL # of valence e- (Subtract 1 e- for every positive charge, and add 1 e- for every negative charge on the molecule.) 2. Determine which atoms are bonded together, put 2 e- into each bond 3. Use the remaining valence e- to complete the octets of the atoms surrounding the central atom 4. If central atom has less than an octet of e-, have a neighbour share e- with the “deficient atom” by putting an extra pair of e- 5. Replace each pair of e- with a dash

VIII.3 BONDING Ex. 1 CH 4

VIII.3 BONDING Ex. 2 NH 4 +

VIII.3 BONDING Ex. 3 O 2

VIII.3 BONDING Ex. 4 NO +

VIII.3 CHEMICAL BONDING Ex. 5 CHO 2 -

O NE LAST TO TRY HPO 2

H OMEWORK ON L EWIS STRUCTURE Homework p. 183 #85 p. 188 # 86a-u