Bonding Class #8

OB: master relative oxidation numbers, review all bonding

for celebration tomorrow

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.

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.

Let’s determine the relative oxidation numbers of the atoms in these molecules…

HCl

CH4

CO2

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

Sulfur dioxide SO2 S+4 O-2 O-2 (0)

Chromate ion CrO4-2 Cr+6 O-2 O-2 O-2 O-2 (-2)

Permanganate ion

NH3

NaOH

KClO3

Carbon monoxide

Carbon dioxide

Dihydrogen sulfate

Nitrate ion

Nitrogen dioxide

Phosphorus trichloride

Sulfur dioxide SO2 S+4 O-2 O-2 (0)

Chromate ion CrO4-2 Cr+6 O-2 O-2 O-2 O-2 (-2)

Permanganate ion MnO4-2 Mn+6 O-2 O-2 O-2 O-2 (-2)

ammonia NH3 N-3 H+1 H+1 H+1 (0)

Sodium hydroxide NaOH Na+1 O-2 H+1 (0)

Potassium chlorate KClO3 K+1 Cl-5 O-2 O-2 O-2 (0)

Carbon monoxide CO C+2 O-2 (0)

Carbon dioxide CO2 C+4 O-2 O-2 (0)

Dihydrogen sulfate H2SO4 H+1 H+1 S+6 O-2 O-2 O-2 O-2 (0)

Nitrate ion NO3-1 N+5 O-2 O-2 O-2 (-1)

Nitrogen dioxide NO2 N+4 O-2 O-2 (0)

Phosphorus trichloride

PCl3 P+3 Cl-1 Cl-1 Cl-1 (0)

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)

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

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

Intermolecular bonding system Jeopardy!

It keeps ammonia NH3 together as a liquid What is hydrogen bonding?

It keeps Br2 bromine a liquid, but iodine I2 a solid What is the electron dispersion force or electron dispersion attraction?

It keeps phosphorus trichloride PCl3 together as a liquid What is the dipole attraction force?

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

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

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.

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

C O

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

C OIt’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.

True or False?

1. Ionic bonds can be double or single bonds

2. Covalent bonds cannot be nonpolar bonds

3. Oxygen molecules have double polar covalent bonds

4. Nitrogen molecules have double nonpolar covalent bonds

5. Hydrogen atoms can make single or double covalent bonds

6. Oxygen atoms must make double bonds ONLY

7. Water is sometimes a straight line molecule by shape

8. Molecules with polar bonds can never be non polar molecules

9. Molecules with nonpolar bonds only can never be polar molecules

10. The weakest intermolecular bond is the dipole force of attraction

True or False? ALL FALSE!!!

1. Ionic bonds can be double or single bonds No, just magnetic ionic

2. Covalent bonds cannot be nonpolar bonds No, F2 or Cl2 are nonpolar

3. Oxygen molecules have double polar covalent bonds No, double nonpolar

4. Nitrogen molecules have double nonpolar covalent bonds No, triple nonpolar

5. Hydrogen atoms can make single or double covalent bonds No, only single

6. Oxygen atoms must make double bonds ONLY No, in water they make 2 singles

7. Water is sometimes a straight line molecule by shape No, always, always bent!

8. Molecules with polar bonds can never be non polar molecules No, CO2 or CH4

9. Molecules with nonpolar bonds only can never be polar molecules No, NBr3

10. The weakest intermolecular bond is the dipole force of attraction No, electron dispersion forces are weakest, watch them in Group 17

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