06 intermolecular forces
- 2. INTERMOLECULAR FORCES The forces between MOLECULES
- 3. INTERMOLECULAR FORCES Ionic bonds Covalent bonds Metallic bonds Dipole-Ion Attraction Hydrogen bonds Dipole-Dipole Attraction Induced-Dipole Forces (Debye Forces) London Dispersion Forces INCREASINGSTRENGTH Van der Waal’s forces
- 4. LONDON DISPERSION FORCES These forces involve molecules that have no polarity INTERMOLECULAR FORCES A subset of Van der Waal’s forces
- 5. INTERMOLECULAR FORCES London dispersion forces Electrons are not stationary in a molecule. Rather, they are free to disperse throughout the molecule. (electrons move freely inside a molecule). By chance, electrons will disperse unevenly and generate a temporary dipole in the molecule. A temporary dipole can induce a temporary dipole in a neighbouring molecule
- 11. INTERMOLECULAR FORCES INDUCED-DIPOLE FORCES (Debye Forces) These forces involve polar molecules attracting molecules that have no polarity A subset of Van der Waal’s forces
- 12. INTERMOLECULAR FORCES Induced-dipole forces (Debye Forces) Induced-dipole forces involve a molecule with a permanent dipole inducing a temporary dipole in a neighbouring non-polar molecule
- 14. DIPOLE-DIPOLE ATTRACTION These forces involve polar molecules INTERMOLECULAR FORCES A subset of Van der Waal’s forces
- 15. INTERMOLECULAR FORCES Dipole-Dipole Attraction Molecules that are polar attract one another (“like attracts like”) H-Cl Cl-H
- 16. INTERMOLECULAR FORCES Dipole-Dipole Attraction Why are some molecules polar (i.e. have a dipole)? Electrons are not always evenly shared
- 17. INTERMOLECULAR FORCES Dipole-Dipole Attraction It’s like hogging the covers… Warmer CoolerWARMTH DIPOLE BRRRRRR mmmmm…
- 18. HYDROGEN BOND These forces are very strong dipole-dipole bonds (and given a different name) These forces are the most significant to biology. INTERMOLECULAR FORCES
- 19. INTERMOLECULAR FORCES Hydrogen bonds These forces exist between molecules with oxygen, nitrogen, and/or fluorine bound to hydrogen. O, N, and F are very electronegative and pull electrons shared with hydrogen towards themselves, producing an unusually strong dipole.
- 22. DIPOLE-ION ATTRACTION These forces involve a charged molecule attracting a polar molecule INTERMOLECULAR FORCES
- 23. INTERMOLECULAR FORCES Dipole-Ion Attraction Polar molecules have partial charges which exert attraction for charged molecules. For example, the partial negative charge on a polar molecule will attract a positively charged ion, and vice versa.
- 25. METALLIC BONDS These bonds exist between metal atoms only. INTERMOLECULAR FORCES
- 26. INTERMOLECULAR FORCES Metallic bonds Metals generally have low electronegativity and “lose” their electrons easily. Metal atoms lose their valence electrons when they “bond” together, thus allowing positively charged metal ions to float in a “sea of electrons”
- 28. INTERMOLECULAR FORCES Metallic bonds The “sea of electrons” explains why metals are -ductile -malleable -shiny -conduct electricity
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- 30. COVALENT BONDS Covalent bonds can hold molecules together too. INTERMOLECULAR FORCES
- 31. INTERMOLECULAR FORCES Covalent bonds Example: Diamonds & quartz
- 32. IONIC BONDS Ionic bonds can hold molecules together too. INTERMOLECULAR FORCES
- 33. INTERMOLECULAR FORCES Ionic bonds Example: Crystal of salt