Tuesday, November 13, 2007

Update for 11/13/2007

Dear All,

Following is the update for today:

Living Environment 1: HW #20 (Due Thursday)
Glencoe - Read pp. 191-200, Do p. 200 Problems #1, 2, 4.
• Quite a number of you have start to write me e-mail to ask about missing HW and assignments.. This is good, remember, start working on those missing works and see if you can hand them to me by the end of this week.. Second marking period is coming to a close..

Regent Chemistry 1: Unit #4 Exam Tomorrow! Study Hard!
• You can hand in the lab write-up #10 by this Friday.

For question #19, remember that:

P1. When going from left to right within a period, the attraction of the positively charged nucleus for the negative electrons increases with increasing atomic number (# of protons) since the valence electrons are all at the same principal energy level. If attraction for valence electrons increases, that means Electronegative value would increase since it measures how strongly an atom will attract the electron in a chemical bond.

P2. When going from top to down within a Group, there are two factors at play: 1) Additional principal energy level means valence electrons are at greater distance from the nucleus, 2) Electron Shielding Effect – as the number of inner electron energy level is increased, the attractive force from the nucleus is being cancelled by these additional inner shell electron clouds. Both would cause less attraction for the outer valence electrons, hence lower Electronegativity value.

Don't forget P3, since this is the reason why some groups are more active than the other...

P3. Octet Rule: In chemical bonding, atoms tend gain or lose electrons to achieve a full valence shell of 8 valence electrons since it’s the most stable e-configuration.


Dr. Liu

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