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Polarity & Lewis Structures

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Presentation on theme: "Polarity & Lewis Structures"— Presentation transcript:

1 Polarity & Lewis Structures

2 Bonds Non-polar covalent – EN difference is 0-0.3
Ionic Bonds- EN difference greater than 1.7

3 Polarity δ+ or δ- H-F bond (electronegativity-H: 2.1and F: 4.0), calculate the difference, the more electronegative atom gets the δ negative charge

4 Examples H—Cl H—C H—H H—O S—Cl Ca and Cl C and S Mg and F N and O
H—H H—O S—Cl Ca and Cl C and S Mg and F N and O O and H S and O

5 Lewis Structure- Covalent Bonds
Shows how valence electrons (v.e.) are shared in a molecule

6 Types of Covalent Bonds
Single Bond- 2 ve- Double Bond – 4 ve- Triple Bond- 6 ve-

7 Octet Rule All atoms want 8 ve- EXCEPT: H- 2ve- and B- 6ve-
There are other exceptions such as S and P

8 How to draw Lewis Structure Step 1
Determine the total number of valence electrons Ex. NF3

9 Step 2 Arrange atoms If there is a carbon in the molecule, carbon will be in the center. If there is no carbon then the least electronegative atom will go in the center The remaining atoms will surround the center atom

10 Step 3 Bond all atoms at least once
Bonding is sharing one valence electron from each atom- uses 2 valence electron Place remaining valence electrons to go around the most electronegative atoms first to agree with octet rule, if extra v.e. put on the remaining atoms

11 Step 4 Check and make sure all atoms follow the octet rule
If not, put in multiple bonds

12 Ionic Bonds Shows the transfer of electrons

13 Determining Lewis Structure
1st – Write out each atom in the chemical formula- Remember the subscript= the # of atoms 2nd – Draw dot structure 3rd -Remove valence electrons from metal and give them to nonmetal using arrows 4th - Write the charges on atoms and new dot structure Example NaCl, MgCl2, and Na2O

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