Wednesday, December 13, 2006
Mid-week
AP: we finally completed our award-winning molecular geometry/orbital hybridization mega-chart (big bucks on eBay). We then revisited delocalized bonding using benzene as a prime example. The bottom line is that ANYTIME you have to draw resonance structures, there is delocalized bonding in the molecule or polyatomic ion.
We can wrap up this unit in the next two days, I think. Then, we can put a dent in the Christmas assignment and go forthwith to Kinetics in January; that would rule.
Regents: we did multiple examples of Lewis dot structures of "normal" molecules; we then began to learn about METALLIC bonding, which involves sharing of loosely bound (low Zeff) valence electrons throughout a lattice of positive nuclei. This arrangement explains the good electrical conductivity of metals. Lots of stuff on the webpage for homework over the next few days.
Honors: we discussed bonding that occurs within ANY molecules (nonmetal to nonmetal): the bonds between the nonmetal atoms are either nonpolar covalent (0.5 or less electronegativity difference) which means that the pair of electrons are equally shared or POLAR covalent (0.6 or higher electronegativity difference) which means that a PARTIAL negative charge (pole) will develop by the MORE electronegative atom and a PARTIAL positive charge (pole) will develop by the LESS electronegative atom.
We then launched into how to draw the Lewis dot structure for ANY molecule or polyatomic ion. FOLLOW THOSE RULES IN ORDER. If you don't, you will fail the next test worse than any other test in your life (you might even get a negative score, no joke). DO NOT do your own thing. Follow the rules VERBATIM. PRACTICE drawing molecules by carefully following the rules.
As I noted in class, there is ONE step missing from the notes: between steps 3 and 4, IF there are any electrons that have NOT yet been included from the total electron count (AFTER the terminal atoms have their octets or duet for H), the REMAINING electrons must be placed IN PAIRS around the CENTRAL ATOM. After you place those remaining electrons around the central atom, DO NOT EVER EVER EVER use those electrons to form double or triple bonds!!!!!!!! You will always get the wrong answer if you do so.
AFTER THAT, go on to step 4, which says to check that the central atom has an octet. If it does not have an octet, you can form double or triple bonds by using the non-bonded pair(s) of electrons FROM THE TERMINAL (NOT THE CENTRAL!!!!!!!!!!) ATOMS ONLY.
We will do many examples over the next two days.
We can wrap up this unit in the next two days, I think. Then, we can put a dent in the Christmas assignment and go forthwith to Kinetics in January; that would rule.
Regents: we did multiple examples of Lewis dot structures of "normal" molecules; we then began to learn about METALLIC bonding, which involves sharing of loosely bound (low Zeff) valence electrons throughout a lattice of positive nuclei. This arrangement explains the good electrical conductivity of metals. Lots of stuff on the webpage for homework over the next few days.
Honors: we discussed bonding that occurs within ANY molecules (nonmetal to nonmetal): the bonds between the nonmetal atoms are either nonpolar covalent (0.5 or less electronegativity difference) which means that the pair of electrons are equally shared or POLAR covalent (0.6 or higher electronegativity difference) which means that a PARTIAL negative charge (pole) will develop by the MORE electronegative atom and a PARTIAL positive charge (pole) will develop by the LESS electronegative atom.
We then launched into how to draw the Lewis dot structure for ANY molecule or polyatomic ion. FOLLOW THOSE RULES IN ORDER. If you don't, you will fail the next test worse than any other test in your life (you might even get a negative score, no joke). DO NOT do your own thing. Follow the rules VERBATIM. PRACTICE drawing molecules by carefully following the rules.
As I noted in class, there is ONE step missing from the notes: between steps 3 and 4, IF there are any electrons that have NOT yet been included from the total electron count (AFTER the terminal atoms have their octets or duet for H), the REMAINING electrons must be placed IN PAIRS around the CENTRAL ATOM. After you place those remaining electrons around the central atom, DO NOT EVER EVER EVER use those electrons to form double or triple bonds!!!!!!!! You will always get the wrong answer if you do so.
AFTER THAT, go on to step 4, which says to check that the central atom has an octet. If it does not have an octet, you can form double or triple bonds by using the non-bonded pair(s) of electrons FROM THE TERMINAL (NOT THE CENTRAL!!!!!!!!!!) ATOMS ONLY.
We will do many examples over the next two days.
# posted by C @ 5:21 PM 
