1 Bond Character and Molecular Polarity How does atom electronegativity affect bond character and...
-
Upload
neil-phillips -
Category
Documents
-
view
504 -
download
18
Transcript of 1 Bond Character and Molecular Polarity How does atom electronegativity affect bond character and...
1
Bond Character and Molecular Polarity
How does atom electronegativity affect bond character and molecular polarity?
Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings
2
The electronegativity value
• measures an atom’s tendency to attract electrons from other atoms
• is higher for nonmetals than for metals
• Why does this happen?
• What is going on in the atom with Coulombic attraction?
Electronegativity
3
Some Electronegativity Values for Group A Elements
Low values
High values
` Electronegativity increases
` E
lectrone
gativity d
ecrease
s
4
A nonpolar covalent bond
• occurs between nonmetals• is an equal or almost equal sharing of electrons• has almost no electronegativity difference (below 0.4)
Examples: Electronegativity Atoms Difference Type of BondN-N 3.0 - 3.0 = 0.0 Nonpolar covalent
Cl-Br 3.0 - 2.8 = 0.2 Nonpolar covalentH-Si 2.1 - 1.8 = 0.3 Nonpolar covalent
Nonpolar Covalent Bonds
5
Nonpolar Covalent Bond
6
A polar covalent bond
• occurs between nonmetal atoms• is an unequal sharing of electrons• has a moderate electronegativity difference (0.4 to 1.7)
Examples: Electronegativity
Atoms Difference Type of BondO-Cl 3.5 - 3.0 = 0.5 Polar covalentCl-C 3.0 - 2.5 = 0.5 Polar covalentO-S 3.5 - 2.5 = 1.0 Polar covalent
Polar Covalent Bonds
7
Polar Covalent Bond
8
Comparing Nonpolar and Polar Covalent Bonds
Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings
9
Ionic Bonds
An ionic bond • occurs between metal and nonmetal ions• is a result of electron transfer• has a large electronegativity difference (above 1.7)
Examples: Electronegativity
Atoms Difference Type of BondCl-K 3.0 – 0.8 = 2.2 Ionic
N-Na 3.0 – 0.9 = 2.1 Ionic
S-Cs 2.5 – 0.7 = 1.8 Ionic
10
Ionic Bond
11
Use the electronegativity difference to identify the type of bond between the following:nonpolar covalent (NP), polar covalent (P), or
ionic (I).
A. K-NB. N-OC. Cl-ClD. H-Cl
Learning Check
< 0.4
Nonpolar covalent
0.4 to 1.7
Polar covalent
> 1.7
Ionic
Electronegativity Difference
12
Some Electronegativity Values for Group A Elements
Low values
High values
` Electronegativity increases
` E
lectrone
gativity d
ecrease
s
13
Not all molecules with polar bonds are polar
You will learn more about this when you study molecular geometry
14
Crosscutting Concepts
Patterns
in chemistry, and other sciences, we are always looking for patterns
you were able to determine a pattern of nature of bonds formed when different atoms interact
15
Crosscutting Concepts
Models
in chemistry, and other sciences, we often use models to help us understand phenomenon
you used a computer simulation to model the effect of changing electronegativity
16
Crosscutting Concepts
Structure and Function
in chemistry, and other sciences, the way an object is shaped or structured determines many of its properties and functions
the structure of a molecule determines if it is polar or nonpolar
17
Nature of Science and Scientific Inquiry
Laws vs Theories
law-behavior of natural phenomenon or generalized relationships under certain conditions
theory-well substantiated explanation of some aspect of natural world
theories do not become laws even with additional evidence
18
Nature of Science and Scientific Inquiry
Data vs Evidence
data-measurements, observations, and findings collected as part of an investigation
evidence-analyzed data and interpretation of the analysis