Tuesday, December 05, 2006
Tuesday recap and test info
AP: we discussed covalent vs. ionic bonds regarding the degree of covalent character in ionically bonded compounds (metal cations to non-metal anions or polyatomic anions) and explained how covalent character develops when high charge density cations distort the electron cloud of a large polarizable anion. There is also appreciable ionic "character" to covalently bonded atoms that have an electronegativity difference of 0.6 or higher.
The polarity of covalent bonds may result in the formation of permanent dipoles in a molecule if:
there is a net PARTIAL positive region of a molecule with a net partial negative region on the opposite region of the molecule
- this usually results from dipoles that are NOT equal and opposite OR dipoles that, due to lack of symmetrical distribution, do NOT cancel out.
We barely began, formally, our monster chart on all of electronic and molecular geometry, orbital hybridization, and molecular polarity. That chart, naturally, will not be on tomorrow's test.
Okay, I've been meaning to do this because, so far, you all (y'all) comprise the fastest, strongest, greatest AP class (don't ever change) in the history of AP classes though there is some room for improvement:
Tomorrow's exam will not involve long-winded explanations of any more periodic trends or anomalies. As usual, the exam WILL cover what we went over in the notes and hw but I do not think that you will have writer's cramp (maybe dot structure drawer's cramp).
So,
- know how to write out the chemical equations of oxides in water and also the amphoteric equations of aluminum oxide in strong acid or in strong base.
- know the physical and chemical properties of the various groups of elements, the empirical formulas that each group forms with other groups (that's Regents-level stuff), and the electron configurations of transition metal ions (FIRST IN- FIRST OUT valence electron rule!)
- know how to draw the correct Lewis dot structure including any and all reasonable (by the rules) resonance structures for any atom, molecule, or ion (even if there is more than one central atom, as in oxalate ion.)
- know how to calculate ( you must SHOW your calculation; the circle method is fine - bring a PENCIL for that part) and apply formal charge in determining the most significant resonance structure for a molecule or ion.
- know how to determine bond order and its relation to bond length AND bond strength (BDE).
- know the rules for electron deficient species, odd-electron molecules, dimerization of odd-electron species, and expanded octets.
-know the different types of bonds and approximate the degree of ionic or covalent character in a covalent or ionic bond, respectively.
I could test some bond angles and geometry but I won't! That will be on the next test when we have more formal experience with such topics.
Study the notes first (from scratch, do the examples that we did in class), then the hw and practice tests.
Honors: we finished the properties of various groups of elements and then we began our new unit on chemical bonding. We discussed the cause/driving force behind the chemical bonding between atoms or between ions: as bonds are formed, there is greater net attraction between the bonding particles; this is potential energy lowering, which is stabilizing.
Tomorrow's test covers:
- The development of the Periodic Table
- The explanation of anomalies in Mendeleev's Periodic Table (NOTE: this came up at extra help, in the file containing the Mendeleev explanation, I incorrectly stated that each Iodine atom has 54 neutrons...that should be 74 neutrons; as in,
mass number = 127 = 53 protons + 74 neutrons.)
- The arrangement of the modern Periodic Table
- General trends and properties of a given element as predicted from its position on the periodic table
- Explanations of any periodic trends covered in the notes
- Physical and chemical properties and characteristics of elements in various groups
- Transition element atoms and ions with respect to electron configurations: VALENCE electrons are lost BEFORE core "d-sublevel" electrons are lost; transition elements are the ONLY elements that CAN lose non-valence electrons because the outermost "d-sublevel" electrons are relatively ever-so-slightly even HIGHER in energy than the valence electrons; therefore, not much energy is required to lose/remove them.
Regents: good work today predicting empirical formulas from compound names and from charges of the cation and anion.
We also discussed polyatomic ions and predicted the formulas of salts of those ions.
We showed the rule: in the formula, put PARENTHESES around the polyatomic ion ONLY IF IT HAS A SUBSCRIPT OF 2,3,4, etc.! NEVER if there is only ONE of the polyatomic ion in the formula.
For example, NaNO3 is sodium nitrate but Ca(NO3)2 is calcium nitrate.
This Thursday, we will have a quiz on the past few days of lessons! Study and practice this stuff.
The polarity of covalent bonds may result in the formation of permanent dipoles in a molecule if:
there is a net PARTIAL positive region of a molecule with a net partial negative region on the opposite region of the molecule
- this usually results from dipoles that are NOT equal and opposite OR dipoles that, due to lack of symmetrical distribution, do NOT cancel out.
We barely began, formally, our monster chart on all of electronic and molecular geometry, orbital hybridization, and molecular polarity. That chart, naturally, will not be on tomorrow's test.
Okay, I've been meaning to do this because, so far, you all (y'all) comprise the fastest, strongest, greatest AP class (don't ever change) in the history of AP classes though there is some room for improvement:
Tomorrow's exam will not involve long-winded explanations of any more periodic trends or anomalies. As usual, the exam WILL cover what we went over in the notes and hw but I do not think that you will have writer's cramp (maybe dot structure drawer's cramp).
So,
- know how to write out the chemical equations of oxides in water and also the amphoteric equations of aluminum oxide in strong acid or in strong base.
- know the physical and chemical properties of the various groups of elements, the empirical formulas that each group forms with other groups (that's Regents-level stuff), and the electron configurations of transition metal ions (FIRST IN- FIRST OUT valence electron rule!)
- know how to draw the correct Lewis dot structure including any and all reasonable (by the rules) resonance structures for any atom, molecule, or ion (even if there is more than one central atom, as in oxalate ion.)
- know how to calculate ( you must SHOW your calculation; the circle method is fine - bring a PENCIL for that part) and apply formal charge in determining the most significant resonance structure for a molecule or ion.
- know how to determine bond order and its relation to bond length AND bond strength (BDE).
- know the rules for electron deficient species, odd-electron molecules, dimerization of odd-electron species, and expanded octets.
-know the different types of bonds and approximate the degree of ionic or covalent character in a covalent or ionic bond, respectively.
I could test some bond angles and geometry but I won't! That will be on the next test when we have more formal experience with such topics.
Study the notes first (from scratch, do the examples that we did in class), then the hw and practice tests.
Honors: we finished the properties of various groups of elements and then we began our new unit on chemical bonding. We discussed the cause/driving force behind the chemical bonding between atoms or between ions: as bonds are formed, there is greater net attraction between the bonding particles; this is potential energy lowering, which is stabilizing.
Tomorrow's test covers:
- The development of the Periodic Table
- The explanation of anomalies in Mendeleev's Periodic Table (NOTE: this came up at extra help, in the file containing the Mendeleev explanation, I incorrectly stated that each Iodine atom has 54 neutrons...that should be 74 neutrons; as in,
mass number = 127 = 53 protons + 74 neutrons.)
- The arrangement of the modern Periodic Table
- General trends and properties of a given element as predicted from its position on the periodic table
- Explanations of any periodic trends covered in the notes
- Physical and chemical properties and characteristics of elements in various groups
- Transition element atoms and ions with respect to electron configurations: VALENCE electrons are lost BEFORE core "d-sublevel" electrons are lost; transition elements are the ONLY elements that CAN lose non-valence electrons because the outermost "d-sublevel" electrons are relatively ever-so-slightly even HIGHER in energy than the valence electrons; therefore, not much energy is required to lose/remove them.
Regents: good work today predicting empirical formulas from compound names and from charges of the cation and anion.
We also discussed polyatomic ions and predicted the formulas of salts of those ions.
We showed the rule: in the formula, put PARENTHESES around the polyatomic ion ONLY IF IT HAS A SUBSCRIPT OF 2,3,4, etc.! NEVER if there is only ONE of the polyatomic ion in the formula.
For example, NaNO3 is sodium nitrate but Ca(NO3)2 is calcium nitrate.
This Thursday, we will have a quiz on the past few days of lessons! Study and practice this stuff.
# posted by C @ 10:13 AM 
