Bonding Class #8

1. Bonding Class #8 OB: master relative oxidation numbers, review all bonding for celebration tomorrow

2. A long, long time ago, in a galaxy, far, far away… This is going to be great! We learned about oxidation numbers, those little positive and negative numbers in the corners of the periodic table, that told us what ratios of atoms to atoms molecular compounds make. Time to revisit them.

3. Hydrogen has a +1 and a -1 oxidation number. Oxygen has only a -2 oxidatoin number. To “make” molecules, you have to combine atoms to atoms, so that the sum of the oxidation number is zero. These are numbers, not ion charges! Since oxygen is only a -2, it will take two +1 hydrogen atoms to make a molecule. That is why the formula is H2O, and that’s why H3O or HO is not a real compound.

4. Let’s determine the relative oxidation numbers of the atoms in these molecules… HCl CH4 CO2

5. Let’s determine the relative oxidation numbers of the atoms in these molecules… HCl H+1 Cl-1 (+1) + (-1) = 0 CH4 C-4 H+1 (-4) + 4x(+1) = 0 CO2 C+4 O-2 (+4) + 2x(-2) = 0

8. Review (push yourself) Name a compound or molecule or formula unit for each type of bond: Single polar covalent Double polar covalent Triple polar covalent Single nonpolar covalent Double nonpolar covalent Triple nonpolar covalent Ionic Resonant Coordinate covalant Breaks octet rule (too small) Breaks octet rule (too big)

9. Review (push yourself) Name a compound or molecule or formula unit for each type of bond: Single polar covalent H-Cl Double polar covalent O=C=O Triple polar covalent NΞC-H Single nonpolar covalent Cl-Cl Double nonpolar covalent O=O Triple nonpolar covalent NΞN Ionic KCl MgO Resonant O3 ozone Coordinate covalant CO Breaks octet rule (too small) H-H Breaks octet rule (too big) PCL5

10. Intermolecular bonding system Jeopardy! It keeps ammonia NH3 together as a liquid It keeps Br2 bromine a liquid, but iodine I2 a solid It keeps phosphorus trichloride PCl3 together as a liquid

11. Intermolecular bonding system Jeopardy! It keeps ammonia NH3 together as a liquidWhat is hydrogen bonding? It keeps Br2 bromine a liquid, but iodine I2 a solidWhat is the electron dispersion force or electron dispersion attraction? It keeps phosphorus trichloride PCl3 together as a liquidWhat is the dipole attraction force?

12. In one sentence explain the difference between bond polarity and molecular polarity. Who has the guts to stand and orate this one?

13. 13

14. Bond polarity is when there is a difference in electronegativity value between two atoms that are bonding. All ionic bonds are polar, but for covalent bonds we have to check table S. Molecular polarity has to do with molecular shape. If a molecule has radial symmetry, it is a nonpolar molecule. A molecule that doesn’t exhibit radial symmetry is polar. A polar molecule water A non polar molecule CCl4

15. In Queens, especially in Ozone Park, you can get on the A train and go to Brooklyn. Then you get off, cross the platform, and go back to Ozone Park in Queens. You can do this over and over all day long, all night long, all for one price. You can resonate back and forth from Queens to Brooklyn. The bonds in ozone O3 resonate back and forth, they are exceptional bonds, but they exist. In reality the bonds are “both” 1½ sized rather than small doubles and bigger single bonds.

16. Once and for all, with a little dot diagram, and one sentence, explain how carbon monoxide bonds together. CO

17. Once and for all, with a little dot diagram, and one sentence, explain how carbon monoxide bonds together. CO It’s called a double polar covalent bond (the bottom 2 pairs of electrons) and a coordinate covalent bond, which means oxygen just “lends” 2 electrons into the mix so carbon “gets” an octet too.

18. True or False? • Ionic bonds can be double or single bonds • Covalent bonds cannot be nonpolar bonds • Oxygen molecules have double polar covalent bonds • Nitrogen molecules have double nonpolar covalent bonds • Hydrogen atoms can make single or double covalent bonds • Oxygen atoms must make double bonds ONLY • Water is sometimes a straight line molecule by shape • Molecules with polar bonds can never be non polar molecules • Molecules with nonpolar bonds only can never be polar molecules • The weakest intermolecular bond is the dipole force of attraction

19. True or False? ALL FALSE!!! • Ionic bonds can be double or single bonds No, just magnetic ionic • Covalent bonds cannot be nonpolar bonds No, F2 or Cl2 are nonpolar • Oxygen molecules have double polar covalent bonds No, double nonpolar • Nitrogen molecules have double nonpolar covalent bonds No, triple nonpolar • Hydrogen atoms can make single or double covalent bonds No, only single • Oxygen atoms must make double bonds ONLY No, in water they make 2 singles • Water is sometimes a straight line molecule by shape No, always, always bent! • Molecules with polar bonds can never be non polar molecules No, CO2 or CH4 • Molecules with nonpolar bonds only can never be polar molecules No, NBr3 • The weakest intermolecular bond is the dipole force of attraction No, electron dispersion forces are weakest, watch them in Group 17

20. Study tonight, and every night.Do the 2 drills in BONDING section on homepage. Monday we celebrate 20 multiple choice from old regents exams, then Draw a few Lewis dot diagrams (also called electron dot diagrams)+ 2 word answer problems