11.09.2010

ANNOUNCEMENTS: 1. There will be a total of 6 quizzes, one everyday 2. If you're absent before a quiz, that quiz will be the one that's dropped 3.You can drop one quiz and retake one quiz 4. We taped in pages 9 to 15

HOMEWORK: Finish pages 11 to 13

Today in class we learned how to make Lewis dot structures for formulas like CH4 or F2 and others like the examples below:

Before drawing the actual structure, Mr. Paek suggests doing N, H, S and B every time because it makes it a lot easier. These letters stand for Need, Have, Share and Bonds. 

• NEED: you put the number of electrons needed to be stable, for most elements it's 8, but for Hydrogen it's 2. Then add all of it together.
• HAVE: the number of valence electrons then add it all up. 
• SHARE: subtract the number of valence electrons from the sum of the electrons needed. 
• BONDS: you divide the number shared by 2.

For example: The formula SeF2

• N= 24 (Se needs 8 electrons and F2 needs 2 sets of 8 because of the subscript "2", so you do 8+8+8=24)
• H= 20 (Se has 6 valence electrons and F2 has 7 and 7 because of the subscript "2", then you do 6+7+7=20)
• S= 4 (N-H or 24-20=4)
• B= 2 (4 divided by 2)

Once you're done with all that, you have to draw the structure.Using the same formula SeF2, Se would be in the center with two F's on either side, it doesn't really matter what side it's on as long as there are two F's. The bonds represent the lines from Se to the F's. Each line representing the number of electrons shared, which in this case is four, so two lines represent four electrons shared. The picture also has to have 20 total electrons in it because of the have. Since the lines already represent 4 electrons, you need 16 more, so you draw dots around the Se and the F's. I know this may sound confusing, but the picture below should make it easier to understand. The formula I used for this example is the first one below:

NEXT SCRIBER: Seena K.

11.8.10

Announcements- 6 QUIZZES this chapter, Chemthink & Webassign MUST be done before class. We picked up the calender and pages 1-8 in class today.

Homework- Pages 1-8, except 3(most finished in class)

Today in class we learned about covalent bonds. We observed the “potential energy curve” with covalent bonds.




Using a graph like this, we explain that when two atoms are moved far apart to close together the potential energy of the two atoms decrease, making the stability (how stable the atoms are) increase. This would make the electrostatic force a proton-electron attraction meaning that one proton from one atom attracts an electron from the other atom.

When the two atoms move from close together to far apart the potential energy of the two atoms would increase, making the stability (how stable the atoms are) decrease. This would cause a proton-proton repulsion meaning that the protons repel as they get too close to each other.

Next in class we talked about naming covalent bonds. Covalent bonds are ONLY nonmetals. You don’t need to worry about figuring out the charges. When naming the first element NEVER has a mono, but the second one will.

We use these prefixes:
1-mono 2-di 3-tri 4-tetra 5-penta 6-hexa


If the element starts in a vowel and the prefix ends in a vowel take out the prefix vowel, for example Carbon Monoxide.

• Here are a few examples of naming covalent bonds:
CO- Carbon Monoxide
CF3- Carbon Tetrafluoride
N2O3- Dinitrogen Trioxide
AsCl3- Arsenic Trichloride

*Remember to still use –ide at the end of second element





When figuring out if it is an Ionic or Covalent bond look for these:

• Polyatomic Ions (SO4-, NO3-, NH4+, etc.)
• Transition Elements (Cu, Fe, Pb, etc.)
• Metals (Ca, Al, Na, etc.)

Here are some examples on figuring out ionic (I) or covalent (C) bonds and writing the formulas:

• Nitrogen Dioxide C NO3
• Copper(II) Phosphide I Cu3P2
• Sulfur Trioxide C SO3
• Chromium(III) Bromide I CrBr3








Next Scriber- Gennah L

11.2.10

Today in class, Mr. Paek went over a lot of important concepts for Thursdays test. He handed out review sheets for unit 4 before a short quiz. The quiz and review sheet went over some of the main ideas like whether or not the certain element will gain or lose an electron, different charges, compounds and chemical formulas.
**Important concepts:
1. Example: Chlorine: Element will GAIN 1 electron to become more stable.
2. Example: Sodium ions and oxide ions: Na2O
3. Example: CaBr2: Calcium Bromide

Some important rules to remember when studying for thursdays tests are the polyatomic ions: ***Sulfate, Nitrate, Phosphate, hydroxide, carbonate, ammonium, bicarbonate

After reviewing and taking the short quiz, we played Ionic Boggle!!! Ionic Boggle (hopefully we can play again!!) is where you try to make compounds with the elements you are given. You play it like boggle the only difference is the letters are now elements!

WEBASSIGN DUE THURSDAY, TEST THURSDAY.
Good luck to everyone on the test!!!! Study hard! :)

11. 1. 2010

• At the beginning of class, Mr. Paek collected any quizzed people needed to take home on Friday and the extra credit unit 4 packets. He also check in the homework that was assigned over the weekend which was pages 9-13 in the journal.
• We went over the homework (pages 9-13) and if people had any questions on the homework they were answered.
• Mr. Paek taught the class a short cut on writing the formulas for compounds. For example if the compound is cobalt (III) carbonate, since cobalt has a charge of +3 and carbonate has a charge of -2, in order to write the formula you can just switch the charge numbers, ex. Co2Ca3
• For the majority of class we worked on our journal pages alone and asked questions as needed.
• At the end of class we took a short quiz testing out ability to write compound formulas and name compounds etc.

Don't forget to read pages 253-258 in the book and answer question number 7 on page 258.

Also we have 2 web assigns.

10.29.10

At the beginning of first period, Mr. Paek tough us a little on ionic formulas and how to figure out the formulas for different compounds. For example, if we had a K+ and a O2- then we would need to get potassium's charge the opposite of oxygen and to equal zero. Here are some other Examples of ionic formulas:

Ex:
Co3+ and Cl- = CoCl3-
K and N= K3N



Mr. Paek also talked about Polyatomic Ions and their symbols. Polyatomic ions are ions that such as Sulfate, Nitrate, Phosphate, Etc... Mr. Paek also went over how to name the formulas Such as CaCl2 would be calcium chloride. He also noted that if there was a roman numeral in front of the first named element that it was the charge. After we walked everything trough we took a quiz on a few things we've already talked about its nothing to worry about. after the quiz Mr Paek assigned some homework.

Homework:
Worksheets handed at beginning of class. pages 11, 12, 13, and 14.

10.13.10

Wednesday: late arrival! :) 35 min period

At the beginning of the period, Mr. Paek showed us a few vidoes on metal reactivity. He explained how the periodic table consists of different families:
Row 1(downward) - Alkali metals
Row 2(downward)- Alkaline earth metals
D Block(sideways)- Transition metals

The vidoes consisted of experiments about the reactions of the alkali metals and water. The farther down the row in the periodic table, the stronger/more intense the reaction. In one of the videos, it included an experiment with a glass. The metals were put in the water one by one:
Li- Floated on the water while giving off hydrogen
Na- The same as Li, but a more vigorous reaction. Na gave off much more hydrogen
K- Produced sparks and a small fire
Rb- Produced bigger sparks and bigger fire
Cs- Completely shattered the glass cup

After watching the vidoes, Mr. Paek introduced a short lab. The metals that were being tested were calcium, magnesium, and aluminum. We placed these metals into well plates and used water, HCL, phenolphthalein indicator (PHTH) (liqiud) to see how they would react with the metals. Her is the data:
Appearance:
Ca- little rocks
Mg- thin metal sheets
Al- Flat rocks

PHTH:
Ca- water turns pink
Mg- magnesium sheet turns pink
Al- water becomes cloudy

Water:
Ca- sizzles and dissolves
Mg- nothing
Al- nothing

HCL:
Ca- sizzles and disolves a little
Mg- sizzles and gives of hydrogen
Al- nothing

PHTH and HCL
Ca- turns pink
Mg- nothing
Al- nothing

NO HOMEWORK!!!
Next Scriber: Sal :)

Friday October-1-2010

To start class Mr. Paek went over the previous days scribe post. Then he started giving us notes in the papers labeled Atomic Models. Then we started the fireworks lab.

PreLab: when electrons drop DOWN an energy level, they give off a specific amount of energy in the form of electromagnetic radiation. This energy then strikes our eye, causing chemical reactions in the eye that excite neurons and thus we perceive color. The electrons for metals in particular have energy levels far enough apart to cause colors in the visible spectrum

What does the statement, “Electrons can become excited,” mean?

The purpose was to observe the different quantum leaps of electrons in several metal salts. Basically at each lab station, there were cups of different salts, metal splints and a Bunsen burner. When we got the splint wet, we covered the end with salt, and stuck it into the flame. Depending on the salt, the flames changed colors like bright red, blue/green and others.

On the lab sheet, you had to describe the specific color given off by each metal salt and the go to the front of the room where Mr. Paek had 3 different unknown salts that he showed us on the bunsen burner and depending on the color and our resulfs from the other lab stations, had to deduct what they were. the bell rang before we finished the post lab questions so Mr. Paek just said we'd go over those on Monday. Happy Homecoming!