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 (: