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Chapter 4

Chapter 4. Covalent bonding. How does H 2 O form?. Oxygen has 6 valence electrons. Does Hydrogen give up its one electron?. +. +. How about H 2 ?. The nuclei repel because of positive charges But they are attracted to electrons They share the electrons. Covalent Bonds.

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Chapter 4

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  1. Chapter 4 Covalent bonding

  2. How does H2O form? • Oxygen has 6 valence electrons. • Does Hydrogen give up its one electron?

  3. + + How about H2? • The nuclei repel because of positive charges • But they are attracted to electrons • They share the electrons

  4. Covalent Bonds • Formed by the attraction of two atoms for a shared pair of electrons. • Neither atom will have a charge. • Molecule - an uncharged group of two or more atoms held together by covalent bonds.

  5. Covalent Bonds • Do nonmetals gain or lose electrons to attain noble gas configuration? • Can two or more nonmetals form a bond? YES!

  6. How? BY SHARING ELECTRONS

  7. F Covalent bonding • Fluorine has seven valence electrons

  8. F F Covalent bonding • Fluorine has seven valence electrons • A second atom also has seven

  9. F F Covalent bonding • Fluorine has seven valence electrons • A second atom also has seven • By sharing electrons

  10. F F Covalent bonding • Fluorine has seven valence electrons • A second atom also has seven • By sharing electrons

  11. F F Covalent bonding • Fluorine has seven valence electrons • A second atom also has seven • By sharing electrons

  12. F F Covalent bonding • Fluorine has seven valence electrons • A second atom also has seven • By sharing electrons

  13. F F Covalent bonding • Fluorine has seven valence electrons • A second atom also has seven • By sharing electrons

  14. F F Covalent bonding • Fluorine has seven valence electrons • A second atom also has seven • By sharing electrons • Both end with full orbitals

  15. Covalent bonding • Fluorine has seven valence electrons • A second atom also has seven • By sharing electrons • Both end with full orbitals F F 8 Valence electrons

  16. Covalent bonding • Fluorine has seven valence electrons • A second atom also has seven • By sharing electrons • Both end with full orbitals F F 8 Valence electrons

  17. Single Covalent Bond • A sharing of two valence electrons. • Occurs between nonmetals and Hydrogen. • Form molecules, NOT ionic compounds.

  18. How to show how they formed • It’s like a jigsaw puzzle. • I have to tell you what the final formula will be. • You put the pieces together to end up with the right formula.

  19. H O Water Each hydrogen has 1 valence electron Each hydrogen wants 1 more The oxygen has 6 valence electrons The oxygen wants 2 more They share to make each other happy

  20. O Water • Put the pieces together • The first hydrogen is happy • The oxygen still wants one more H

  21. O Water • The second hydrogen attaches • Every atom has full energy levels H H

  22. Multiple Covalent Bonds Atoms can share more than one pair of electrons - single covalent bonds (2 e-) - double covalent bonds (4e-) - triple covalent bonds (6e-)

  23. O Carbon dioxide • CO2- Carbon is central atom( I have to tell you) • Carbon has 4 valence electrons • Wants 4 more • Oxygen has 6 valence electrons • Wants 2 more C

  24. O Carbon dioxide • Attaching 1 oxygen leaves the oxygen 1 short and the carbon 3 short C

  25. O O Carbon dioxide • Attaching the second oxygen leaves both oxygen 1 short and the carbon 2 short C

  26. O O Carbon dioxide • The only solution is to share more C

  27. O O Carbon dioxide • The only solution is to share more C

  28. O Carbon dioxide • The only solution is to share more O C

  29. O Carbon dioxide • The only solution is to share more O C

  30. O Carbon dioxide • The only solution is to share more O C

  31. Carbon dioxide • The only solution is to share more O C O

  32. Carbon dioxide • The only solution is to share more • Requires two double bonds • Each atom gets to count all the atoms in the bond O C O

  33. Carbon dioxide • The only solution is to share more • Requires two double bonds • Each atom gets to count all the atoms in the bond 8 valence electrons O C O

  34. Carbon dioxide • The only solution is to share more • Requires two double bonds • Each atom gets to count all the atoms in the bond 8 valence electrons O C O

  35. Carbon dioxide • The only solution is to share more • Requires two double bonds • Each atom gets to count all the atoms in the bond 8 valence electrons O C O

  36. How to draw them • Add up all the valence electrons. • This is the number you have to work with • Use the guess and check method until all atoms have 8 electrons (except H and He) • Some electrons will be shared

  37. Examples • NH3 – N is central • N - has 5 valence electrons • H - has 1 valence electrons N H

  38. Examples • HCN C is central atom • N - has 5 valence electrons • C - has 4 valence electrons • H - has 1 valence electrons • Total of 10 electrons

  39. Another way of indicating bonds • Often use a line to indicate a bond • Called a structural formula • Each line is 2 valence electrons H O H H O H

  40. Structural Examples • C has 8 electrons because each line is 2 electrons • Ditto for N • Ditto for C here • Ditto for O H C N H C O H

  41. Interparticle Forces

  42. Interparticle Forces • Forces in molecular compounds are weaker than those in ionic compounds.

  43. Molecular Compounds • Usually not soluble in water • Do not conduct electricity well (Why not?) • Usually liquids or gases at room temperature

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