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Lecture 54

CHEM 107 Lecture Notes - Lecture 54: Trigonal Pyramidal Molecular Geometry, Molecular Geometry, Ionic CompoundPremium

2 pages99 viewsSpring 2017

Department
Chemistry
Course Code
CHEM 107
Professor
Mallory Monique Mentele
Lecture
54

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4-20-17-Polarity
Thursday, April 20, 2017
11:01 AM
Ionic compounds have an electronegativity difference of 2 or greater
Covalent compounds have an electronegativity difference between 0 and 2
Covalent polar compounds have an electronegativity difference between 0.4 and 2
***THE ELECTRONEGATIVITY DIFFERENCE BETWEEN H AND C IS VERY LOW
-we count that as a nonpolar bond
C-H bonds are nonpolar
*Look at picture on phone
Practice Problems
Use a polar arrow to indicate the polarity of each bond
N--H, F--N, I--Cl
Rank the following bonds in order of increasing polarity
H--N, H--O, H--C
*Look at picture on phone
Molecular Polarity
-To determine overall molecular polarity, you must look at individual bonds AND
molecular geometry
*Look at picture on phone
Dipole Moments and Molecular Polarity
Nonpolar
1. Two identical polar bonds pointing in opposite directions will cancel
2. Three identical polar bonds at 120 degrees from each other will cancel
3. Four identical polar bonds in a tetrahedral arrangement (109.5 degrees from each
other) will cancel
Polar
1. Two polar bonds with an angle of less than 180 between them will not cancel
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