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Chapter 9: Chemical Bonding I: Lewis Theory. CHE 123: General Chemistry I Dr. Jerome Williams, Ph.D. Saint Leo University. Overview. Covalent Bonding Electronegativity & Polarity. Covalent Bonding.
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Chapter 9: Chemical Bonding I: Lewis Theory CHE 123: General Chemistry I Dr. Jerome Williams, Ph.D. Saint Leo University
Overview • Covalent Bonding • Electronegativity & Polarity
Covalent Bonding • Covalent Bonding results from sharing of at least one pair of valence electrons between atoms.
Covalent Bonding • Every covalent bond has a characteristic length that leads to maximum stability. • This is thebond length.
Covalent Bonding • Energy required to break a covalent bond in an isolated gaseous molecule is called thebond dissociation energy. • Energy is released when new bonds are formed.
Electronegativity & Polarity • Bond polarity is due to electronegativity differences between atoms. • Pauling Electronegativity: is expressed on a scale where F = 4.0
Electronegativity & Polarity • % Ionic Character: As a general rule for two atoms in a bond, we can calculate an electronegativity difference (∆EN ): ∆EN = EN(Y) – EN(X) for X–Y bond. • If ∆EN < 0.5 the bond is covalent. • If ∆EN < 2.0 the bond is polar covalent. • If ∆EN > 2.0 the bond is ionic.
Electronegativity & Polarity • Using electronegativity values, predict whether the following compounds are nonpolar covalent, polar covalent, or ionic: • SiCl4 CsBr FeBr3 CH4 • HCl CCl4 NH3 H2O