Monday, February 28

Today we started off class by going over the Chapter 7.0-1a WebAssign.
The answers are as follows:

1. Ionic bonds normally involve two elements giving or taking electrons and consist of a cation and anion. Covalent bonds share their electrons with another element and can involve a cation and anion or two anions.

2. A
3. D
4. A
5. A
6. D
7. B and C
8. C: 4 F: 7 S:6 Cl: 7
9. Bonds are formed by a pair of electrons being shared among atoms.
10. a. 1, 3 b. 2, 2 c. 3,1 d. 4,0
11. 2, 4, 6
12. a. 8 b. 14 c. 18 d. 10 e. 24 f. 32 g. 14 h. 24
13. It is usually the atom listed first and it is usually the lone atom.

After we went over the WebAssign answers, Mr. H showed us the Lewis Structure Rules:

1. Count # of valence electrons

2. Draw skeletal structure

3. Give each atom 8 electrons (except H-2e-, B-6e-)

4. Count electrons (dots and dashes) if needed, make corrections

Also for 3 and 4 this is trial and error which means if the number of valence electrons you are given don't match up with how many you drew, you must go back and make the necessary corrections.

We then began our lesson for the day on page 5 in our packets.

The first few problems involved basic Lewis Structure questions that were fairly easy to solve. However, the problems became harder and we couldn't solve them with only using single bonds. For CO2 there are 4 V.E. for carbon and 12 for oxygen, 6*2=12, and in total there are 16 V.E. If you do this problem the regular way, you will get an incorrect answer of 20 when the problems states you only need 16. To fix this problem you have to use 2 double bonds bonding the 2 oxygen atoms to the central carbon atom. The result is four V.E. around each oxygen and two double bonds which equal 8 connecting to carbon, and you have 4+8+4=16.

We did a couple more of these types of problems and then went on to problems that broke the octet rule. For XeF4, there are a total of 36 V.E., but when you draw the Lewis Structure, you can only put in 32. To solve this problem you have to satisfy the octet rule for all atoms and put the remaining electrons on the central atom which is usually the larger one.

Once we finished this, Daria told Mr. H to shut up so we could present our skits about bonding. They were all good and provided useful information about some of the bonding rules.

The last thing we did before class ended was go over WebAssign 7.1b and the answers are as follows:

1. A

2. False

3. C

4. To determine which one of the two competing Lewis structures is the more reasonable structure.

5. A

6. B

7. ABCE

Our homework is the 7.2 Reading WebAssign due tomorrow.