11.16.10

ANNOUNCEMENTS: We took a quiz today, pick up pages 21-24 if you were not here, and I think that is it.

HOMEWORK: Page 24

Today we learned about different types of bonds that are related to electronegativity. Electronegativity as you may remember, describes an element's tendency to "hog" electrons (pull them closer to themselves than the other atom). We got a periodic table that has each element's electronegativity.

The three different bonds we learned were:

Purely covalent/non-polar: In this bond, neither atom has that much of a stronger pull than the other. The difference between the electronegativites of the two atoms will be 0.0-0.4

(*To find the electronegativity difference just subtract the smaller electronegativity from the larger one. EX: Carbon has an electroneg. of 2.5, Hydgrogen has an electroneg. of 2.1 so the difference is .4 This would be a non-polar covalent bond.)

Polar covalent: One atom has a slightly larger electroneg. causing it to have a stronger attraction to more electrons. Difference of electroneg. is 0.5-1.6

(EX: Hydrogen is 2.1, Oxygen is 3.5. The difference is 1.4 so it is polar covalent.)

In both of these, electrons are shared.

Ionic: In an ionic bond, one atom has a significantly larger attraction to the electrons than the other. In this case electrons are transferred. The range for this is 1.7 or greater.

(EX: Sodium is .9 and Flourine is 4.0 The difference is 3.1 so it is ionic)

We also learned how to identify atoms with a partial positive and a partial negative charge.

The atom with the greater electronegativity will have a partial negative charge because there are more electrons going towards it. And the partial positive atom has the smaller electronegativity because there are less electrons attracted to it.

Mr. Paek taught us the symbol that is used for this.

Disregard the second picture, he did not teach us that. The S looking thing is the symbol. If it's partial negative then a - sign will follow the symbol. And if its partial positive then it will be a + sign. In this image, hydrogen has an electronegativity of 2.1 and flourine has one of 4.0 Because flourine's electroneg. is greater, more electrons are attracted to it so it has a partial negative charge.

That's all folks!

Oh and the next scriber shall be Jillian (:

October 1, 2010

ATOMIC STRUCTURE: In class on Friday we defined a few terms that have to do with atoms.

Proton- It has a positive charge and its location is in the nucleus (Remember Proton is Positive)

Neutron- Neutral, it has no charge. Its location is in the nucleus as well.

Electron- Located outside the nucleus. They have a negative charge



We also learned some stuff that has to do with the PERIODIC TABLE.

-The number located above the element's symbol is the atomic number. It represents the number of protons



-The number below the symbol is the atomic mass. That stands for the number of protons PLUS the number of neutrons.



*An atom will usually have the same number of protons and electrons. When those numbers are the same, it has no charge. The only way an atom can get a positive or negative charge is by losing or gaining electrons.

EXAMPLE:

Oxygen's atomic number is 8. Therefore it has 8 protons as well as 8 neutrons. If oxygen were to GAIN 2 electrons(making its total 10 electrons), then it would have a -2 ion(charge) because it has two more electrons than protons. On the other hand, if it were to LOSE two electrons (making its total electrons be 6), then it would have a +2 ion because it has two more protons.



ATOMIC MODELS:

We learned some stuff about orbitals and relative energy and other stuff with Bohr's model, but I did not quite undestand much of that thus, I would explain it poorly. Please be sure to ask Mr. Paek about that stuff.



FIREWORKS LAB:

The purpose was to observe the recations of 7 different salts when they were exposed to fire.

PRE LAB: When electrons drop down an energy level, they give off a specific amount of energy. The energy hits our eyes, excities our neurons, and then we see color.

QUESTION: What does the term "electrons becoming excited" mean?

ANSWER: Energy is added to the electrons so they jump energy levels.



Materials: 7 salts, sticks, water, Bunsen Burner.

Procedure: 1.First we wet the stick a bit in the water

2. Then we dipped it in the salt

3. We placed it over the Bunsen Burner (while it was lit) and observed the reaction

4. Then recorded it in our table



Results:

• Li+(Lithium) Gave off a hot pink color


• Na+(Sodium) Gave off a orange color that looked like fire


• K N O3 Gave off a dull green


• K Cl Gave off a dull purple


• Sr2+ (Strontium) Was red orange


• Cu(Copper) gave off a very dull green (almost white looking)

And Cu2+ was an emerald green

At the end we has three "mystery salts" and had to figure out which ones they were based on the results of the colors we got.

Postlab:

Why did each metal salt give off a different color? That's because they had different numbers of electrons and they each went to different energy levels.

NEXT SCRIBEPOST WILL BE: Zak