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Warm Up:. Octet Rule. a filled layer contains 8 electrons Exceptions (After bonding…) H and He will have 2 Beryllium will have 4 Boron will have 6 Some transition metals can have more than 8. Dot Diagrams for Molecules.
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Octet Rule • a filled layer contains 8 electrons • Exceptions (After bonding…) • H and He will have 2 • Beryllium will have 4 • Boron will have 6 • Some transition metals can have more than 8
Dot Diagrams for Molecules • Atom with most unshared electrons goes in middle *capable of forming most bonds* • Count to make sure you have the right number of electrons • Each atom wants to have a full valence • Try these… • CH4 O2 CO2 • NH3 N2 H2O
Write the shapes of each of the dot diagrams you made before
Warm Up: Label the following bonds as polar and nonpolar. • Br2 • HCl • H2 • CH4 • NH3
Dipole • Molecule with an overall unequal distribution of electrons
Two atom molecules • If the bond is non-polar, so is the molecule • If the bond is polar, the molecule has a dipole and is polar
Do these molecules have dipoles? • N2 • O2 • CO • HF
Three atom molecules • If the 2 polar effects are equal and oppositely directed, the molecule is nonpolar • Otherwise, the molecule is polar water Carbon dioxide
Four atom molecules • It is possible that the 3 polar effects may cancel and produce a nonpolar molecule • It is also possible that they don’t cancel and produce a polar molecule NH3 (ammonia) Exception to octet rule
Five atom molecules • It is possible that the 4 polar effects may cancel and produce a nonpolar molecule • It is also possible that they don’t cancel and produce a polar molecule CH4 CH3Cl
Intermolecular Forces • Between molecules • Dipole-dipole • Hydrogen bonding • Van der Waals
Dipole-Dipole • Like electrical charges and magnets, dipoles can attract one another • Stronger attractions with stronger dipoles • Stronger attractions when molecules are closer together with lower temperature and higher pressure
Hydrogen Bonding • Occurs when Hydrogen and Fluorine, Oxygen, or Nitrogen are present • FON • Ammonia, hydroflouric acid, water • Higher boiling points with hydrogen bonding
Van der waals • Recall that electrons have a little bit of freedom to move around their electron clouds • VDW are produced by momentary uneven electron distributions • Extremely weak • Responsible for bonding of nonpolar molecules, liquefaction of inert gases, 3 phases of halogens at STP • Stronger for molecules with more electrons • Gets stronger as molecules get closer