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Covalent Bonding

Covalent Bonding. Chapter 9. Now, let’s talk about SHARING electrons. Or, a COVALENT BOND!. 1. Covalent Bonding. Cmpd formed called molecule ; Ex: C 12 H 22 O 11 CO 2 share valence electrons Usually elements that are close together Usually 2 NM.

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Covalent Bonding

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  1. Covalent Bonding Chapter 9

  2. Now, let’s talk about SHARING electrons. Or, a COVALENT BOND!

  3. 1. Covalent Bonding • Cmpd formed called molecule; • Ex: C 12 H 22 O 11 CO 2 • share valence electrons • Usually elements that are closetogether • Usually 2 NM

  4. Biology Connection • Most covalent bonds are: Macro moleculesPurposeElem 1. 2. 3. 4. All elements have _______ in common.

  5. 2. How to Form C-B • Ex: H 2 Drawn: • e- dot for each (also called _________) • Draw circles around each elem (at the top) to share valence electrons

  6. Try: • NH 3 ammonia • Also called _______________ • Draw e- dot for each element (use white board first) • Draw as a structural formula go

  7. .. H-N- H H Lone Pairs go

  8. Lone Pairs • Unshared electrons • What could they potentially do? • Bond w/ another element go

  9. Covalent Bonds Sharing electrons to fill the outer most shells of both the hydrogen atoms and the oxygen atom = now everyone is “happy”. go

  10. Covalent Bonds go

  11. Nonpolar Covalent Bonds: Dogs of equal strength (equal sharing!)

  12. Diatomic Elements Beside part #2 • Ex (name all 7):

  13. 7 rule There is 1 extra on here

  14. Could be: • Single bond C-C (easier to break) • Double bond C=C • Triple bond C= C (harder to break) (single bond prod elem far apart, double is closer, etc. The “longer the bond length gives it strength”) go

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  16. Double and Triple bonds • Helps economizee- • Cmpd won’t bond with as many dif atoms • ADD: The energy to break a covalent bond is called Bond Dissociation Energy

  17. Organic Cmpds • Organic compounds • Means natural, living, C-based

  18. 3. Dashes or Dots? -------- represent valence e- in a bond; 1 pr (2 e-) .. Represent unshared electrons End of pg 1

  19. 4. Three 3 Exceptions to Octet • < 8 val e-  Be Sn B Ex: BF3

  20. > 8 val e-  P As S -Noble gas config? s2p6 -where do extra e- stay? 3 d Ex: SF4

  21. Odd total # of electrons -usually N -ex: NO No octet? No Is it stable? No

  22. 5. Properties • Low MP & BP • No ions  neutral b/c they share e- • Electrolyte? No • Crystal lattice weak  called covalent network • Phases: mostly S some L

  23. 6. Drawing structural formulas/Lewis Structures AB 2 E 2 A is central atom -usually least electronegative (carbon always central) (electroneg on the left) Hydrogen is never central element -lowest # of atoms

  24. AB 2 E 2 B is terminal atom (side) -usually mentioned 2nd -more eleneg; on right -bigger # of atoms

  25. AB 2 E 2 E called lone e- or lone prs go on central atom

  26. A little advice on Lewis Structures: 1. Form bonds between atoms (2 e-). 2. Distribute remaining e- to give each atom an octet (recall exceptions). 3. If there aren’t enough e- to go around, form double or triple bonds. examples

  27. NH3 • ammonia • N: 5 x 1 = 5 val e- • H: 1 x 3 = 3 total val e- • total = 8 total val e- for both N & H • N is central

  28. N2 • nitrogen gas • N: 5 val e- x 2 N’s = • 10 total electrons

  29. Those on your paper: 1. 2. 3. 4. 5.

  30. 6. 7. 8. 9.

  31. NH4+ : ammonium ion

  32. SO42- : sulfate ion • 5 x 6 = 30 • total = 30 + 2 = 32 OH- : hydroxide ion • 6 + 1 + 1 = 8 total

  33. Those on your paper: 10. 11. 12. 13.

  34. Resonance Structures • ADD-resonance – bonding between atoms that cannot be represented on Lewis structure • (It shows all possible structures) End of page 2

  35. Electronegativity Chart

  36. Electronegativity & Polarity • Recall e- affinity: • Electronegativity: ability to attract e- • Helpful to determine bond type • How? Take difference b/w elements Use eleneg chart; F= _____; what is least eleneg?______ PT

  37. Covalent can be: • Polar • e- pulled: • Oppositely charged: • Stronger e- attraction: • Usually 2 ______ elements • Use “partial charge” symbol to show + & - charges as e- are pulled to one atom

  38. Ex: H – Cl Written: or Also called:Dipole-Dipole -attraction b/w opposite charged atoms on polar mole. go

  39. go

  40. Nonpolar • Atoms in bond pull: • Usually 2 of the ________ element • Ex:

  41. Nonpolar Covalent bonds– electrons are being shared EQUALLY!! Oxygen Atom Oxygen Atom Oxygen Molecule (O2)

  42. Electronegativity Scale • Used as a guide 0 4 Try samples at the bottom of the page using the chart on the next slide.

  43. Ex: Electronegativity Chart

  44. **Covalent bonds are usually _____________ b/w 2 dif elem **__________ w/ individual elem; Ionic is ___________

  45. Polarity and Solubility • Polar and Ionic usually solbule in polar substances • Rule: “Like dissolves like” Physical property

  46. Intermolecular Forces Also called van der Waals forces • Covalent • Vary in strength • Weaker than ionic • 3 types

  47. They lead to prop of covalent bonds: • ______ MP & BP • Exist as ______/or vaporize easily • _______ solids (like paraffin wax, pencil)

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