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Chapter 8

Chapter 8. Bonding. Lewis Structures. Diagram that shows American chemist Gilbert N. Lewis Dots = Paired dots = Simple way of showing electrons Most reactions involve only. Lewis Structures. When drawing: Use electron configuration Move in clockwise direction… “12” = s orbital

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Chapter 8

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  1. Chapter 8 Bonding

  2. Lewis Structures • Diagram that shows • American chemist Gilbert N. Lewis • Dots = • Paired dots = • Simple way of showing electrons • Most reactions involve only

  3. Lewis Structures • When drawing: • Use electron configuration • Move in clockwise direction… • “12” = s orbital • “3, 6, 9” = p orbitals – fill each with ONE electron before filling with pairs… • Just like orbital filling diagram… • Examples: draw Lewis Structures of B, N, F, Ne

  4. The Ionic Bond • Ionic bond: • Transfer of electrons from • Ions form with • Attraction between electrostatic charges is a strong force which holds atoms together

  5. The Ionic Bond • NOT A • Bond not just between (for example) one sodium and one chloride

  6. The Ionic Bond • Typically • Metals usually • Nonmetals usually

  7. Predicting Formulas of Ionic Compounds • In almost all stable chemical compounds of representative elements, each atom attains a • This concept forms the basis for our understanding of chemical bonding.

  8. Predicting Formulas of Ionic Compounds • How many electrons must be gained or lost to achieve noble gas configuration? • Ba must lose • Forms the ion • S must gain • Forms the ion • So…must be ratio of

  9. Predicting Formulas of Ionic Compounds • Elements in a family usually form compounds with the same atomic ratios • Because they have the same number of valence electrons • Must gain or lose the same number of electrons • See table 11.4 pg 233

  10. Predicting Formulas of Ionic Compounds • The formula for sodium oxide is Na2O. Predict the formula for • Sodium sulfide

  11. Predicting Formulas of Ionic Compounds • Rubidium Oxide • Rubidium • Oxygen • So…formula must be • This makes sense b/c rubidium is in same family as sodium

  12. The Covalent Bond • A pair of • Most common type of bond • Stronger than • Electron orbital expands to include both nuclei • most often found between • Negative charges allow positive nuclei to be drawn close to each other

  13. The Covalent Bond • Atoms may share more than one pair of electrons • Double bond – • Triple bond – • Multiple bonds are • Covalent bonding between identical atoms means electrons are shared • Covalent bonding between different atoms leads to

  14. Electronegativity • The attractive force that an atom of an element has for • Atoms have different electronegativities • Electrons will spend more time near atom with • So…one atom assumes a partial • The other assumes a partial

  15. Electronegativity • Electronegativity trends and periodic table • See table 11.5 page 237 • Generally increases from • Decreases • Highest is • Lowest is

  16. Electronegativity • Polarity is determined by difference in electronegativity • Nonpolar covalent • Polar covalent • Ionic compound

  17. Electronegativity • If the electronegativity difference is greater than • Above • Below

  18. Electronegativity • Polar bonds form between two atoms • Molecules can also be polar or nonpolar • Dipole • Polar • Nonpolar

  19. Lewis Structures of Compounds • Convenient way of showing ionic or covalent bonds • Usually the single atom in a formula is the central atom

  20. The Ionic Bond • LEWIS STRUCTURES of ionic bonds

  21. The Covalent Bond • LEWIS STRUCTURES of covalent bonds • Use dashes instead of dots…

  22. The Covalent Bond

  23. Lewis Structures of Compounds • Obtain the total number of valence electrons • Add the valance electrons of all atoms • Ionic – add one electron for each negative charge and subtract one electron for each positive charge

  24. Lewis Structures of Compounds • Write the skeletal arrangement of the atoms and connect with a single covalent vond • Subtract two electrons for each single bond • This gives you the net number of electrons available for completing the structure

  25. Lewis Structures of Compounds • Distribute pairs of electrons around each atom to give each atom a noble gas structure • If there are not enough electrons then try to form double and triple bonds

  26. Lewis Structures of Compounds • Write the Lewis Structure for methane CH4

  27. Lewis Structures of Compounds • Carbon Dioxide, CO2

  28. Complex Lewis Structures • Some molecules and polyatomic ions have strange behaviors… • No single Lewis structure is consistent • If multiple structures are possible the molecule shows

  29. Complex Lewis Structures • Carbonate ion, CO32-

  30. Compounds ContainingPolyatomic Ions • Polyatomic ion: • Behaves as a single unit in many chemical reactions • Sodium carbonate (Na2CO3)

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