1. VSEPR Theory: Molecular Shapes Most shapes are based on a __________________. Examples: CH 4 CCl 4 Removing the top of the tetrahedral makes the ________________ shape. Examples: NH 3 PCl 3 tetrahedral pyramidal

2. VSEPR Theory: Molecular Shapes Removing one side of the pyramid makes the _____________ shape. Examples: H 2 O H 2 S If there are only two atoms bonded, it is ______________. Examples: O 2 HCl CO 2 (linear because of its double bonds.) bent linear

3. VSEPR Theory: Molecular Shapes Another we will need to know is called “trigonal planar”. “Trigonal” means that the central atom is bonded to ___ other atoms. “Planar” means that the 3 atoms all lie in the same ______________. Example: BF 3 (Notice that Boron will only have ___ e - ’s around it. The missing pair of electrons will make it planar instead of ________________.) 3 plane 6 pyramidal

4. VSEPR Theory: Molecular Shapes Finally, the last 2 shapes occur when there are 5 or 6 regions of electrons are around the central atom. (These molecules are also exceptions to the octet rule!) - ___________________ (5 electron domains) - __________________ (6 electron domains) Examples: PCl 5 and SF 6 Trigonal bipyramid Octahedral

5. Polar and Nonpolar Bonds Even though the electrons in a covalent bond are shared, sometimes the attraction for the bonded pair, (the _____________________), is uneven. This gives rise to 3 bond types. nonpolar covalent bonds: ____________ sharing of the e - pair polar covalent bonds: ________________ sharing of the e - pair ionic bonds: a ___________ of e - ’s from the metal to the nonmetal How To Determine the Bond Type Bond type is based on the electronegativity _____________ between the two bonded atoms. electronegativity equal unequal transfer difference

6. Figure 12.4 The three possible types of bonds. nonpolar polar ionic

7. Polarity of Molecules One side is slightly (__) and the other side is slightly (__). Polar molecules are also known as _______________. Polarity depends on the __________ and symmetry of the molecule. symmetrical molecules (looks the same on all sides)= ___________ asymmetrical molecules = ___________ Polar molecules are moved by ____________ charges. +– dipole shape nonpolar polar static

8. Molecular Polarity Practice Problems: Determine if the following molecules are polar or nonpolar based on their shape. a) CH 4 b) NH 3 c) H 2 O d) HCl e) BF 3 symmetrical tetrahedral asymmetrical pyramid asymmetrical bent asymmetrical linear symmetrical trigonal planar nonpolar polar Dipole of NH 3 Dipole of H 2 O

9. Bond Dissociation Energy This is the energy needed to ___________ the bond. Generally, the longer the bond, the _____ energy it takes to break it. Single bonds take ________ energy to break than double bonds and triple bonds require the _________ energy to break. When bonds form, energy is _____________. (Breaking bonds requires the addition of energy.) released less most break

10. Bond Dissociation Energy

11. Intermolecular Attractions The __________ attractions between one molecule and another are called _______ ______ ________ forces. They cause gas particles to stick together and _______________ at low temperatures. weak Van der Waals condense

12. Dispersion Forces There are two types of intermolecular forces: (1) ____________________ forces: (the weaker type) – caused by random _______________ motion – generally _____________ with ________ electrons in the molecule Dispersion electron strongermore − exist between all types of molecules − This force causes Br 2 to be a liquid and I 2 to be a solid at room temperature.

13. Dipole Interaction Forces (2) ____________ interactions: (the stronger force) – caused by the attraction of the (__) side of one polar molecule and the (__) side of a different polar molecule Dipole + –

14. Hydrogen Bonds ________________ “Bonds” are a special type of dipole interaction. This attraction between molecules is not a chemical bond. Electrons are not being shared or transferred. They occur between the hydrogen of one polar molecule and the ____, ___ or ___ of another polar molecule. Hydrogen Bonding in Water Hydrogen N O F

15. Hydrogen Bonds The ladder rungs in a DNA molecule are hydrogen bonds between the base pairs, (AT and GC).

16. Intermolecular Forces At Work Substances that contain stong intermolecular forces have a ________ melting point and a _________ boiling point. Liqids containing strong intermolecular forces have higher surface tension and a higher viscosity. higher

17. Surface Tension

18. Properties of Ionic Compounds and Covalent Molecules Molecular: ________________ of electricity formed between two _______________ usually have ________ melting points solubility in water _______: (polar =dissolve; nonpolar = insoluble) forms ______________________solids. Insulators nonmetals low varies covalent crystalline

19. Properties of Ionic Compounds and Covalent Molecules Ionic:  _______________ of electricity when dissolved water or melted.  formed between __________ and _________________  have _________ melting points  usually ________ soluble in water form ___________________ solids Conductors metalsnonmetals high very ionic crystalline (dissolved salt)