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L13S08 CovalentBond Resonance

L13S08 CovalentBond Resonance - L 13"Covalent Bonding...

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Unformatted text preview: L 13: "Covalent Bonding, Resonance, Formal Charge Lewis Electron Dot Structures Valence Electrons Stable Octet Previously : : : : : : : : : : : Ionic Bonding (Electron Transfer) e- + - Coulomb : : : : : + + :F: H . He : . . . Li. Be . .B . . C . .N . : O . : F. :Ne : . . . . . . Na. Mg. .Al . .Si . . . . :S . : Cl . :Ar: P Mg. . . : : 2000 A.P ines M.Kubinec UCB L3-1 Attraction Covalent Bonding (Electron Sharing) Molecular Orbitals : : Li. + : F. Li + + Na. + : Cl. 2000 A.Pines M.Kubinec UCB Octet Rule H H C H H : : : : : : : :N :C : : : : O N: O: Na :Cl : - MgCl2 L3-4 Exceptions :F O B F: : : : : : : : : :F: F .. Xe F .. : F H. + : : : : .H : : H:H : Cl: Cl : : : : : : : 2004 M.Kubinec, A. Pines 2000 A.Pines M.Kubinec UCB :Cl . + . Cl : H Cl: Cl: H N H H .. F SF6 : : ChemQuiz 12.1 Which is the correct Lewis electron dot structure of formaldehyde? : : : : : : L3-6 L13-1 L3-7 2000 A.Pines M.Kubinec UCB H 2004 M.Kubinec, A. Pines L13-2 : A) C::O ::O B) C:::O: :::O : H C) H:C:O:H More electronegative element captures e- Ionic: Summary + Li :F: Chemical Bonding : : : : Resonance, Bond Order Ozone : : : : +O H H CH2O Electronegativity Electrons shared equally Covalent: :Cl: Cl : + Dipole, symmetry Dipole, No Dipole Dipole O O+ - O- -O O O C O -2 O O C 1 O 1 3 O 1 : : : : : : - Polar Covalent: Unequal sharing, Dipole moment + Carbonate - O O C O O OC O - - O O - O H Cl: Cl: : : Benzene L4-4 2000 A.Pines M.Kubinec UCB L3-11 2001 UC Regents (`covalent' electron distribution) Formal Charge : : : : Lewis Dot Structure: Share electrons equally: .N . (5) Compare to atoms: Lewis Dot Structure: O: N :O: O: (7) Divide up electrons: (More electronegative captures e-) N (2) : : O: N :O: : : - (`Ionic' electron distribution) Oxidation Number - : : :O: (8) : : O: (6) : : : : .N . (5) 0 O: (6) Compare to atoms: .N . (5) +3 : : Formal Charge: 2001 UC Regents 2004 M.Kubinec, A. Pines -1 L4-11 Oxidation number: 2001 UC Regents -2 L13-3 L4-10 2004 M.Kubinec, A. Pines 1 L 13: "Covalent Bonding, Resonance, Formal Charge Chemical Bonding Ionic: More electronegative element captures e- + Li :F: Covalent: Polar: Unequal sharing, Dipole moment Electrons shared equally :Cl: Cl : : : : Electronegativity : : : : : - + Dipole, symmetry Dipole, No Dipole Dipole + H Cl: Cl: : : : : 2004 M.Kubinec, A. Pines L13-4 ChemQuiz 13.1 + - Which of the following molecules is does not have a dipole moment? A) C O B) O=C=O O C) H C H 2004 M.Kubinec, A. Pines L13-5 Resonance, Bond Order Ozone O - O O C O O O C - O O O C O O O C 1 O 2- 1 3 Carbonate - O O O O - - O O - O O 1 Benzene 2004 M.Kubinec, A. Pines L13-6 2004 M.Kubinec, A. Pines 2 L 13: "Covalent Bonding, Resonance, Formal Charge ChemQuiz 13.2 How does the NO bond order change in the process: nitrite O N O O NO2 - nitrate N O3 - O O N A) Increase 2004 M.Kubinec, A. Pines B) Same C) Decreases L13-7 (`covalent' electron distribution) covalent' Formal Charge : : Lewis Dot Structure: Share electrons equally: .N . (5) Compare to atoms: O: N :O: : : - : : O: (7) .N . (5) 0 : : : : O: (6) Formal Charge: 2004 M.Kubinec, A. Pines -1 L13-8 (`covalent' electron distribution) covalent' Possible Lewis Dot Structures for OCN-: Formal Charge [:O C N:]- [:O C N:]- [:O C N:]N:] N:] N:] FC: -1 Minimize formal charges Negative charge on most electronegative atom 2004 M.Kubinec, A. Pines L13-9 2004 M.Kubinec, A. Pines : : : : : : : : : 0 0 0 0 -1 +1 0 -2 3 L 13: "Covalent Bonding, Resonance, Formal Charge ChemQuiz 13.3 How does the Formal Charge of nitrogen change for the process: NO2 - O N - O NO3 - O N O O 1) Increase 2004 M.Kubinec, A. Pines 2) Same 3) Decreases L13-10 Oxidation Number (`Ionic' electron distribution) Ionic' : : Lewis Dot Structure: Divide up electrons: (More electronegative captures e-) O: N :O: N (2) : : - :O: (8) : : : : O: (6) : : Compare to atoms: .N . (5) +3 Oxidation number: 2004 M.Kubinec, A. Pines -2 L13-11 Lecture Complete 2004 M.Kubinec, A. Pines L13-12 2004 M.Kubinec, A. Pines 4 ...
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