Bonding

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Bonding

  1. 1. Intramolecular Intermolecular Types of Bonding
  2. 2. Definitions Bond: a type of interaction between atoms that result in atoms staying close together Molecule: two or more atoms held together by a covalent bond Intramolecular: forces of attraction within a molecule (e.g. intramurals) Intermolecular: forces of attraction between molecules in a compound (e.g. international)
  3. 3. Types of Interactions Summary Intermolecular Intramolecular
  4. 4. Intramolecular Bonds Electronegativity: attraction of an atom for electrons Example of a very electronegative atom: oxygen When two atoms with different electronegativity get together…
  5. 5. Intramolecular Bonds
  6. 6. Intramolecular: Ionic If two atoms with very large differences in electronegativity get together, one of atom could take away an electron from the other Acceptor “stealer” of electron becomes negativity charged (anion = negative ion) Donor of electron becomes positively charged (cation = positive ion)
  7. 7. Intramolecular: Ionic Ionic bond forms from an attraction between an anion and cation Ionic compounds are formed by ionic bonds Salts are ionic compounds (e.g. Na+ + Cl-  NaCl) Salt crystals have a 3D lattice because of +/- attractions
  8. 8. Types of Interactions Summary Intermolecular Intramolecular Covalent Ionic
  9. 9. Intramolecular: Covalent  Covalent bond forms when atoms share electrons  Nonpolar covalent bond  atoms have the same electronegativity  electrons are equally shared  e.g. H2  Polar covalent bond  atoms have slight differences in electronegativity  electrons are unequally shared  e.g. HCl
  10. 10. Polar Covalent Bond
  11. 11. Which MOLECULES are polar?
  12. 12. Shape of molecule Why is the molecule CO2 nonpolar when it has a polar covalent bond?
  13. 13. Polarity of a Molecule Bond Shape Nonpolar bond Polar bond Symmetrical nonpolar molecule (e.g. H2) nonpolar molecule (e.g. CO2) Asymmetrical nonpolar molecule polar molecule (e.g. HCl, H2O) Polarity dependent on the polarity of the bond AND the molecular SHAPE
  14. 14. Activity Classify the molecules given into 3 categories: Ionic Polar nonpolar
  15. 15. Types of Interactions Summary Intermolecular Intramolecular Nonpolar Covalent Covalent Ionic Polar Covalent
  16. 16. Intermolecular Forces
  17. 17. Types of Interactions Summary Intermolecular Intramolecular Nonpolar Covalent Covalent Ionic Polar Covalent London (dispersion) forces Dipole-dipole Hydrogen bonding & Ion-dipole
  18. 18. London Dispersion Exists between all molecules Weak force, due to instantaneous diploes
  19. 19. Dipole-Dipole Exists between polar molecules Due to permanent dipoles
  20. 20. Hydrogen Bonding Strong force (just a very strong dipole-dipole) between a H-atom and an electronegative atom Specifically requires 2 polar molecules having: an H-atom covalently bonded to an O, N or F an O, N or F covalently bonded to an H
  21. 21. Ion-Dipole Dipole is attracted to an oppositely charged ion When ionic compounds dissolve in water, water molecules surround the ion and remove it from the crystal lattice structure (hydration shell)
  22. 22. Hydrophobic Interactions Nonpolar molecules are excluded from mixing with polar molecules by associating with each other Minimizes the surface contact between non- polar molecules and polar molecules.
  23. 23. Hydrophobic Interactions Can occur spontaneously without the need for energy Example: oil molecules spontaneously associate excluding water
  24. 24. HW Question Compare polar covalent bond and dipole-dipole force. Use an example. [3 marks]  Note: In any compare question there must be a reason why the 2 items being compared were chosen. Your answer should address the relevance of the 2 items to each other. If there is no relationship between the 2 compare items, then the question itself would be pointless.

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