UNIT VIIILewis 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…

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C. Writing Lewis Structures

a. Simple Ionic Compounds:Draw the Lewis Structure of:

a) MgO

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b)KCl

 c) CaF2

 

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b. Covalent Compounds:

Octet Rule: most atoms, other than hydrogen, tend to attain an octet of electrons as a result of forming covalent bonds

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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

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Ex. 1CH4

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Ex. 2NH4

+

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Ex. 3 O2

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Ex. 4 NO+

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Ex. 5 CHO2

-

ONE LAST TO TRY

HPO2

HOMEWORK ON LEWIS STRUCTURE

Homework

p. 183 #85 p. 188 # 86a-u