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intermolecular forces.ppt.pptx

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RaniaMohamed726883

This document discusses and compares different types of intermolecular forces: 1) Dispersion forces, also called London forces, are the weakest and occur between all molecules due to instantaneous dipoles. Larger molecules have stronger dispersion forces. 2) Dipole-dipole forces occur between polar molecules and are stronger than dispersion forces due to partial charges. Hydrogen bonding is the strongest type of dipole-dipole force. 3) Hydrogen bonding, which occurs between hydrogen and fluorine, oxygen, or nitrogen, is the strongest type of intermolecular force due to large partial charges. It is essential in molecules of life like DNA and proteins. Ionic bonds are the strongest overall due

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intermolecular forces.ppt.pptx
We have been working on intramolecular force (forces in bonds). Intermolecular forces- forces which hold full molecules together. -ionic molecules have the strongest attraction due to their full positive and negative charges. -this high electromagnetic attraction (+ and -) results in ionic molecules staying more tightly together than covalent molecules. = higher melting point for ionics!
Covalent intermolecular forces: (we will go weakest to strongest) 1) Dispersion force- -Often called London Force after Fritz London. -weakest of three covalent forces. -only force that keeps non- polar molecules together since they have no true + or - attraction. But dispersion forces occur in all molecule types. -the larger the molecule, the more dispersion force it will have (more electrons).
2) Dipole-Dipole Force- -stronger than dispersion forces. -occurs in weaker polar molecules because of their partial positive and negative charges. (隆+ and 隆-) animation Draw HCl and show charges. H隆 +Cl隆 - H隆 +Cl隆 - H隆 +Cl隆 - -dipole-dipole is for all polar molecules except H-F, H-O or H-N. (they have a stronger force)
3) Hydrogen Forces- strongest IM covalent bond -Hydrogen forces are a lot of FON (hydrogen with F,O and N only) -the EN is so great between H and FON that the whole molecule has a very strong 隆+ and 隆- end. H = 2.1 F = 4.0 EN = 1.9 (is almost ionic!!!)
-these stronger 隆+ and 隆- ends create a greater force than dipole-dipole which has weaker partial charges. Ex. Water -hydrogen forces are essential for making the molecules of life DNA and proteins.
Weakest Strongest Dispersion (London) Dipole- Dipole Hydrogen forces Ionic bonds (electromagnetic) Melting point Lowest highest

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intermolecular forces.ppt.pptx

  • 2. We have been working on intramolecular force (forces in bonds). Intermolecular forces- forces which hold full molecules together. -ionic molecules have the strongest attraction due to their full positive and negative charges. -this high electromagnetic attraction (+ and -) results in ionic molecules staying more tightly together than covalent molecules. = higher melting point for ionics!
  • 3. Covalent intermolecular forces: (we will go weakest to strongest) 1) Dispersion force- -Often called London Force after Fritz London. -weakest of three covalent forces. -only force that keeps non- polar molecules together since they have no true + or - attraction. But dispersion forces occur in all molecule types. -the larger the molecule, the more dispersion force it will have (more electrons).
  • 4. 2) Dipole-Dipole Force- -stronger than dispersion forces. -occurs in weaker polar molecules because of their partial positive and negative charges. (隆+ and 隆-) animation Draw HCl and show charges. H隆 +Cl隆 - H隆 +Cl隆 - H隆 +Cl隆 - -dipole-dipole is for all polar molecules except H-F, H-O or H-N. (they have a stronger force)
  • 5. 3) Hydrogen Forces- strongest IM covalent bond -Hydrogen forces are a lot of FON (hydrogen with F,O and N only) -the EN is so great between H and FON that the whole molecule has a very strong 隆+ and 隆- end. H = 2.1 F = 4.0 EN = 1.9 (is almost ionic!!!)
  • 6. -these stronger 隆+ and 隆- ends create a greater force than dipole-dipole which has weaker partial charges. Ex. Water -hydrogen forces are essential for making the molecules of life DNA and proteins.