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Bonding Lewis Structures: Ionic and Covalent Bonds

Learn about Lewis structures and how they are used to represent ionic and covalent bonding. Understand the concepts of electronegativity, polarity, and the formation of multiple bonds. Explore examples of Lewis structures for various compounds and polyatomic ions.

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Bonding Lewis Structures: Ionic and Covalent Bonds

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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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