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Electronegativity Differences and Bond Types (Bond Character) Difference in Electronegativity Bond CharacterExample Nonpolar covalentH-H (0.0) > Moderately polarH-Cl (0.9) Very polarH-F (1.9) ≥ 2.0IonicNa + Cl - (2.1)
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Polar Bonds and Molecules (8.4)
• Bond Polarity• Bond polarity has to do with unequal
distribution of shared electrons• This causes one end of the bond to have a
“partial positive” (δ+) charge and the other to have a “partial negative” (δ-)charge
• These types of bonds are called polar covalent bonds and are said to possess a dipole moment
What causes bond polarity?
• A polar bond results from a difference in electronegativity between the bonded atoms
• The greater the difference, the more polar the bond is
• The degree of polarity depends upon the difference in electronegativity
Electronegativity Differences and Bond Types (Bond Character)
Difference in Electronegativity
Bond Character Example
0.0-0.4 Nonpolar covalent H-H (0.0)
> 0.4-1.0 Moderately polar H-Cl (0.9)
1.0-2.0 Very polar H-F (1.9)
≥ 2.0 Ionic Na+ Cl- (2.1)
Effect of Bond Polarity on Molecules
• Polar bonds may result in polar molecules• Bond character (nonpolar, polar, ionic) affects– How molecules interact with one another– Physical properties of substances
Polarity of Molecules
• A molecule as a whole has a dipole depending upon
• The presence of polar bond(s)• The geometry of a molecule• Examples:– CH4
– CO2
– H2O