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Covalent Bonding: Nature, Names, and Shapes

Learn about the nature of covalent bonds, how to name covalently bonded groups, molecular shapes, characteristics of covalent molecules, and how to compare polar and nonpolar molecules.

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Covalent Bonding: Nature, Names, and Shapes

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  1. CHAPTER 9 Covalent Bonding

  2. What You Will Learn… • The nature of the covalent bond • How to name covalently bonded groups of atoms • Shapes of molecules • Characteristics of covalent molecules • How to compare and contrast polar and nonpolar molecules

  3. Why It Is Important • Most compounds are covalently bonded • Including those in living organisms

  4. Assignment • Write out Chapter 9 vocabulary words and their definitions • 14 words on page 271 • PLUS the octet rule from Chapter 6

  5. The Covalent Bond Section 9.1

  6. Objectives • Apply the octet rule to atoms that bond covalently • Describe the formation of single, double, and triple covalent bonds • Compare and contrast sigma and pi bonds • Relate the strengths of covalent bonds to bond length and bond dissociation energy

  7. Covalent bond Molecule Lewis structure Sigma bond Pi bond Endothermic Exothermic Key Terms

  8. Review • Do noble gases bond? • Why or why not? • What is an ionic bond? • Fill in the blank: • In an ionic bond, electrons are_________from one ion to another.

  9. What if both atoms need valence electrons?

  10. Sharing Electrons • Another way atoms acquire noble gas configurations • Occurs when BOTH atoms want to gain valence electrons

  11. What is the Octet Rule from Chapter 6?

  12. Covalent Bond • Bond that results from sharingvalence electrons • Shared electrons become part of BOTH atoms’ outer energy level • Most between NONMETALS

  13. Covalent vs Ionic

  14. Molecule • Formed when two or more atoms bond covalently • Covalent bonds are often called molecular bonds

  15. Diatomic Molecules • Two atoms of the same element form a bond • Attractive forces = Repulsive forces • Examples: • H2 • O2 • N2 • Halogens: F2, Cl2, Br2, I2

  16. Diatomic Fluorine Each Fluorine has 3 lone pairs and 1 shared pair of electrons

  17. Single Covalent Bond • 2 electrons (or 1 pair) are shared between two atoms

  18. Single Covalent Bond

  19. Lewis Structure • Electron-dot diagrams for molecules • Dots represent lone pairs of electrons • A line represents shared electrons

  20. Lewis Structures H-H H ö: H

  21. Lewis StructuresGroup 7A Elements 7 valence electrons, need 1 more, form one single bond

  22. Lewis StructuresGroup 6A Elements • 6 valence electrons, need 2 more, form 2 single bonds

  23. Lewis StructuresGroup 5A Elements • 5 valence electrons, need 3 more, form 3 single bonds

  24. Lewis StructuresGroup 4A Elements • 4 valence electrons, need 4 more, form 4 single bonds

  25. Practice Problems

  26. Practice Problem • Section 9.1 #1 on page 874

  27. Sigma Bond • Another name for single covalent bonds •  • Electron pair is shared in the area centered between atoms • Valence orbitals overlap end to end • s and s; s and p; p and p

  28. Multiple Covalent Bonds • Atoms form noble gas configuration by sharing more than one pair or electrons between 2 atoms • C, N, O, S

  29. Double Bond • 2 pairs (or 4 electrons) of electrons are shared

  30. Triple Bond • 3 pairs (or 6 electrons) of electrons are shared

  31. Pi Bond • Formed when parallel orbits overlap to share electrons • Shared par occupies the space above and below the line that represents where the 2 atoms join together

  32. Multiple Bonds • 1 sigma bond • At least 1 pi bond

  33. Double Bond • 1 sigma bond • 1 pi bond

  34. Triple Bond • One sigma bond • Two pi bonds

  35. Pi and Sigma

  36. Strength of Covalent Bond • Distance between nuclei • Bond length= distance at maximum attraction • Bond dissociation energy= energy required to break bonds

  37. Exothermic Reaction • More energy is released forming new bonds than is required to break bonds in the initial reactants

  38. Endothermic Reaction • Greater amount of energy is required to break the existing bonds in the reactants than is released when the new bonds form in the products

  39. QUESTIONS?

  40. Homework • 6-12 on page 247 • Bonding Problems

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