Chemblog!

Thanks to an industrious and innovative member of our AP Chem Dream Team, you now have yet another resource to help you understand and ace AP Chem. Take advantage of the collective genius of the class.
Here is the link to our newly created forum:
http://z8.invisionfree.com/AP_Chemistry/index.php

This is a fine idea and I hope that you all continue such a resource among your peers in college.

I ("the horse's mouth") may occasionally visit the forum (I already posted a reply) but I will mainly be available to help you as usual at extra help and via email.

Happy 2007!

I posted a TON of extra help files to guide you through your Christmas break assignment; use them as needed over the next week and before the next exam. You now have literally hundreds of practice problems with extensive solutions and explanations! Take advantage of this wealth of information. We will not be spending much time in class reviewing the material that you did over this break; however, you will be thoroughly tested on the material from the break so make sure that your independent study is intensive. Send me an email if you have any problems with the topics. I also posted the gas labs. The lab write-ups are due on Jan. 8 ; the data is supplied (copy the data into your lab notebook).

I'd like to thank the awesome AP class for giving me a Christmas present: on your Bonding II exams, almost all of your work on the extensive charts on the many variations of molecules and ions ( AX3, AX4E, AX2E3, etc) was perfect! Regarding these molecular geometry charts, I have never seen such a level of unanimously excellent work from any past AP class. I know that the expertise that I witnessed did not happen without A LOT of practice, which is the key to success in this course. So, congratulations and kudos to you all! On the AP Chem exam, the bonding/molecular geometry question should be a cakewalk for you all.

What is "osmotic pressure"? Here's a video from a chem prof that will help you and here is a flash animation that clearly demonstrates what occurs at the particle level.
This site has a nice, brief discussion and example of the van 't Hoff factor, "i" (now I see, the " ' " goes before the "t" in Dutch names; Jacobus Henricus van 't Hoff was born in Rotterdam, The Netherlands; with a name like that, he better have discovered something; the rest is history.)

Here are two sample problems in which "i" is determined and explained .

Our short-awaited vacation is here!! Good times. This year is flying by and we will return strong in '07.
Naturally, we have some hw over the vacation: reinforcement material for Regents and Honors so that you can recall what you already know; some new and some review material for AP.


Regents and Honors classes : From our class webpage, download each "learning module" powerpoint (you must email me if you have any trouble doing so), read the lessons, then write the questions and answer the questions BEFORE you look at the answers as you go through the powerpoints. Show any necessary work (reasoning or calculation) that you did to get your answer. It's fine (no points off) if you initially get the problem wrong. You can just put a line through your original answer and then write in the correction. Don't cheat yourself out of doing this properly; you need to master this material for the Regents exam so that you can ace that test. Also, you will see some of these questions on upcoming exams. Label (by module title) and organize your papers before you hand them in. The assignment MUST be done NEATLY, CLEARLY, and (ultimately) ACCURATELY; your grade will be based on those criteria.
Over the long break, I will also be posting some general review powerpoints, question and answer sets, and even some PODCASTS that I found that coincide with our textbook. That's just in case you need or want some more review. Update: The podcasts are posted. They were created by an upstate Chem teacher; the podcasts are from 8 to 25 minutes long, depending on the unit or section. The podcast numbers coincide with the Chapters and Sections of our textbook. Why not download these to your "iPod" and listen to them on your way to and from Grandma's house? Why not listen to them with Grandmama?

AP: It's all you for Chapters 11 and 12. Don't hesitate to email me if you have a question on how to do something but make sure that you first have read the text/study guides and looked at/solved the sample questions.
Later, I will post some more solved problems which will be categorized by question type and I will post a link or two to help guide you.

I won't be in until 8:10 AM tomorrow so, if you have extra help questions, see me then before A period begins.

Regents and Honors: have your labs ready tomorrow; lab folders will be inspected. Students who are not current and accurate with their labs will have to stay after EVERY DAY until they perfectly complete and make up all labs.

AP: I will also have a Christmas break lab write-up for the butane and hydrogen labs that we almost did.
:)

Regents: Bonding test class average: 82 - still waiting for improvement...
Congrats to those who came to extra help; that small group scored in the 90s.

Honors: two minutes into today's exam, I saw unfathomable errors being written by an unbelievable number of students! Right NEXT to the words "ionic bond" were drawn COVALENTLY BONDED ATOMS! In other words, COMPLETE CONTRADICTIONS! Most explanations completely missed the main point and, instead, focused on minor or non-factors. That's like arguing that colds are caused by "the cold weather" instead of by viruses! The Lewis structures were atrocious; as I told you ad infinitum, follow the five steps and you will be right every time, do not follow the steps and you will always be wrong. The simplest task of all, to distinguish a polar from a non-polar covalent bond, could not even be done consistently. That skill requires FIRST GRADE level comprehension. Clearly, some of you did not even look at the notes, have notes, or take notes for the past two weeks. Some of you are not doing the homework and are "learning" nothing but distortions and contradictions, which is WORSE than learning NOTHING. Only about one out of ten students managed to write down the information as it appeared in the notes and was explained in class, on-line, and in the homework. That's not a high bar to clear, but so few have done so.

AP: so far so good with the Bonding/Molecular geometry exams. You already are at a huge advantage with your ability on this topic. Just be sure to maintain your expert knowledge in this area. Of course, I will be giving you lots of review questions so that you can stay sharp. (raspy voice: "good times")

AP: I hope that you found today's exam palatable. Most years, the results are more than decent on this exam; not that the exam is easy but this exam tests skills that can be perfected after a few days of practice.
Tomorrow, I will suspend our current unit (intermolecular attractions) and do some of the more difficult problems from Chapters 11 and 12, which are assigned over the break.
I will be putting up a RIDICULOUS number of problems with worked out solutions to help guide you through the two units and, of course, I am an email away, if you need assistance.

Honors: thanks to a couple of students who pointed out a couple of errors on the polyatomic ion worksheet and one error on the salt-naming worksheet. I will correct those errors and post them tonight (on the class webpage, look for the words "updated file" next to the file name.
Today, we went over some of the test-taking errors from the last test. Own your mistakes, (in LIFE, there is seldom better advice than this!), correct them, and learn from them so that you can improve and grow academically.
Then, we reviewed the stock system, which MUST be used for salts of transition metals (very few exceptions: Ag, Cd, Zn salts).
We also learned how to name hydrated salts (HYDRATES) in which there is a certain integer ratio of water molecules embedded in the ionic lattice per formula unit of the salt.

IN D PERIOD but NOT G PERIOD, we finished with the PREFIX system for naming molecules. NO SALTS (except hydrates) HAVE PREFIXES SO, IF YOU EVER SEE A PREFIX IN A FORMULA, YOU MUST BE LOOKING AT THE NAME OF A MOLECULE i.e. carbon dioxide..."di" indicates "must be a molecule". NOTE: unlike salts, there is NO "geometric lattice" of atoms in a molecule; each individual molecule is a separate, unique, individual entity. For example, every separate, individual carbon dioxide molecule has EXACTLY ONE carbon ATOM (double) bonded to TWO oxygen ATOMS, one oxygen atom on either side of the carbon atom. The Lewis structures of molecules show an actual individual molecule but the Lewis structures of salts cannot and do not depict the entire lattice of ions. Lewis structures of salts ONLY show one FORMULA UNIT of the ionic lattice, so Lewis structures of salts cannot possibly depict the true number of ionic bonds per cation or anion that actually exists in even the tiniest speck of the salt lattice.

Now, to name a molecule, put the appropriate prefix (1-mono, 2-di, 3-tri, 4-tetra, 5-penta, 6-hexa, 7-hepta, 8-octa, 9-nona, 10-deca) in front of each element in the molecule based on the number of atoms of each element that makes up one single molecule. IF there is ONLY ONE of the first (less electronegative) element in the formula, do NOT use the prefix mono. Notice that you never have called CO2, "monocarbon dioxide" SO DON'T START doing so! However, if you have only one of the second element, you MUST use the "mono" prefix, as in CO is carbon monoxide (notice, in most cases of two of the SAME vowel, you can delete the first vowel, i.e. it's not carbon monooxide).

Since we did not cover naming molecules in G Period, NEITHER Honors class will be tested on naming MOLECULES. The test material will go up to and including naming hydrated salts, hydrates.
Test-taking tip for tomorrow: write out the prefixes for 3=tri and 4=tetra; I DON'T KNOW WHY but, every year, students mix up those two prefixes! That kills me! "Tri" does not look like or even sound like "four"! Immediately AFTER the test begins, write out any other prefixes or facts/info (stored in your short term memory from having looked at your notes BEFORE you enter the classroom) that you are afraid that you might forget during the test.
The test covers all material covered in class since the beginning of the Bonding Unit notes (note: knowledge and mastery of atomic structure and the periodic table is automatically necessary to understand this unit) up to and including naming molecules via the PREFIX system (NOT molecules via the Stock system). Use the notes as a list of objectives.
Don't ever forget (again) : SLOW DOWN when you read each question (and STOP underlining every word in the question, that is WORSE than underlining/identifying no key words and as indiscriminate/useless as underlining no key words!) and make sure that you know exactly and only what is asked for. This will prevent you from (again) writing irrelevant and/or superfluous information. If you do not TAKE PAINS to answer exactly and only what is asked for, you will then (again) run out of time for writing down lines of information that earn you nothing. If you are still unsure about how much to write, do NOT take chances with "how" or "why" questions. Keep asking yourself "how" or "why" and keep writing down info, pictures (with reference), and calculations that support your explanation.

Regents: we did several examples of naming hydrated salts (hydrates) and began the PREFIX system for naming molecules. Tomorrow's multiple choice exam will cover everything that we have done so far in the Bonding Unit up to and including naming molecules via the prefix system.
Make SURE that you have done all of the hw and practice worksheets in preparation for this test. Just as with Honors, the following test-taking tip applies:
For tomorrow: write out the prefixes for 3=tri and 4=tetra; I DON'T KNOW WHY but, every year, students mix up those two prefixes! That kills me! "Tri" does not look like or even sound like "four"! Immediately AFTER the test begins, write out any other prefixes or facts/info (stored in your short term memory from having looked at your notes BEFORE you enter the classroom) that you are afraid that you might forget during the test.
Tip 2: The secret to taking multiple choice tests is to initially IGNORE the answer choices (except for math questions). Work out the solution to the question and then see whether there is a matching answer choice. If there is not, you did something wrong (or, ask me whether you have a misprinted test- it can happen!). If a choice matches your carefully worked out answer, you are likely to have avoided any trap answers and you should be confident about your choice. This assumes that you CAREFULLY read the question and identified the key terms that tell you what is actually being asked for; so, the MOST important test-taking tip on ANY test is to read each question slowly and carefully- even read the question twice, once at a casual speed and the second time at a slower speed.
Good luck tomorrow!

Here's another good website that shows how to determine a compound's name from its chemical formula and vice-versa.
http://dbhs.wvusd.k12.ca.us/webdocs/Nomenclature/Nomenclature.html

There is one thing that shows up in a few examples that you should ignore on this site:
the "-ic" and "-ous" suffix naming system for transition metals and for molecules. Though, even today, many chemical manufacturers still put such names on their chemical containers, that naming system is considered too informal. The modern "Stock system" is the internationally used system and will be the only system that is used on the Regents (even AP is almost 100% switched over to the newer standard) and on our tests.
Just FYI, it is good to have seen the old system; it's quite easy to figure out. For example, Copper can form either a 1+ or a 2+ cation. In compounds of Cu 1+, we now say,
for example, copper I chloride; in the "old-skool" system, we would call that cuprOUS chloride. In compounds of Cu 2+, we now say, for example, copper II chloride; in the "old-skool" system, we would call that cuprIC chloride. So, if there is more than one possible ion for a transition metal, "ous" goes with the lower ionic charge of any given transition metal, and "ic" with the higher ionic charge of any given transition metal. Simply, "ous" has been replaced with the lower possible cation charge number and "ic" has been replaced with the higher possible cation charge number.

Here is a good website with images of Lewis structures and images of atoms, molecules, and ions.

I changed the paper chromatography lab due date to Wednesday. Your test day is on Tuesday so, if you need to put off working on the lab until after school on Tuesday, you can still get the lab done on time. Wednesday, we won't have time to do anything but joke, reminisce, sing, and cry but I will have you compile your lab folders on that day. I will then check all of your folders to see that your labs are neat, complete, and accurate. You have until Wednesday to make sure that your lab write-ups and folders are done correctly and in order (please pass the word to those who STILL have never seen this web-log; unbelievable).
Warning: If you have been negligent with your lab write-ups , you automatically fail the second quarter. DON'T let that happen! You can ALWAYS complete the lab write-ups with my assistance AT extra help! That's right, I want you to learn from these labs and not make up bogus answers. I'll even stay after school on Wednesday, although before that, I'll be at a faculty Christmas "gathering" until about 2PM. If you already are failing and not handing in the labs, there is always the bonus bad news that you won't be able to take the Regents and you will have to repeat the entire course, not over the summer, but next year. Good times. So, don't shoot yourself in the foot, get the job done by Wednesday so that you can start the New Year right.

Okay, on the class website, there is a RIDICULOUS number of practice questions/files with answers as well as tutorials for Monday's bonding test.

For our test on Monday:
Most of our time and therefore most of our test will be on all of the types of molecules or ions that we drew out in our grand chart. So anything and everything on that chart will be asked for.
Be able to show the orbital hybridization that occurs on a CENTRAL atom starting with the orbital diagram of the un-hybridized atom. Then show the electron shifts that occur in order to form the proper bonding arrangement in the molecule. For example, in CH4, carbon has a valence electron configuration of 2s2 2p2, which had only two unpaired electrons available for bonding. Not only that, the unpaired p electrons are in perpendicular p orbitals. So, in order to explain the four bonds that form in a tetrahedral arrangement, the C must hybridize its 2s and all three 2p orbitals to form FOUR equal energy, tetrahedrally oriented sp3 orbitals. As bonds form, these sp3 orbitals overlap with the Hydrogen 1s orbital (that is all that H has occupied with one electron; generally don't worry about hybridization of terminal atoms unless there is only one type of hybridization that can apply) and the opposite spin electron pairs (one from each atom in this case) form a bond between each pair of atomic nuclei.

For intermolecular attractions, know the different types: induced dipole, dipole-dipole, and extreme dipole-dipole (hydrogen bonding) attractions. Based on electronic and molecular geometry from your Lewis structure and VSEPR, predict the molecular polarity and the expected dominant intermolecular type of attraction. For example, CF4 has tetrahedral electronic and molecular geometry, which results in a symmetric distribution of charge/electrons. The molecule is therefore nonpolar because there is, on average, no net partial positive or partial negative "side" of the molecule so its intermolecular forces of attraction are induced dipole attractions.


Know how to reproduce the molecular orbital diagrams from the starting atomic orbitals. Check out the text and powerpoint to check your diagram. Remember the first FIVE diatomics in period two (from left to right) are the "feminine-shaped" diagrams (ladies first) and the last three O2, F2, and Ne2 are the "masculine-shaped" diagrams. Know how to predict bond order, bond length, bond strength/BDE, para or diamagnetism from the diagrams of these diatomic molecules OR ions. Here is a great site for pictures and review of MO Theory:
http://www.chem.latech.edu/~upali/chem281/281GRCc3.htm
Here's another good site that walks you through most of the bonding subtopics with nice graphics:
http://highered.mcgraw-hill.com/sites/0073656011/student_view0/chapter10/essential_study_partner.html

The text sections 10.5 and 10.6 gets into MO Theory (the answer to those sections' questions are posted now) and there is the Bonding II study guide that has MO theory and questions.

AP: we talked about how molecular orbitals can form from atomic orbitals as atoms bond to form a molecule. This theory is an alternative model for looking at how electrons are distributed throughout a molecule and what specific energies those electrons have. So, it is the same as the quantum mechanical model of an atom as applied to the molecule. The theory predicts bond order, molecular polarity, paramagnetism (in O2, which shows the success of the model), and other physical and chemical properties. However, getting pictures and solving for the energies of electrons in particular molecular orbitals requires sophisticated math and supercomputers. So, we just intro the topic by applying the theory to diatomic molecules.
We also showed that, for OXOACIDS, each "H" in the formula IS NOT BONDED TO THE CENTRAL ATOM but rather to one of the Oxygen terminal atoms, which is why they are called oxoacids. So, in nitric acid, the H is bonded to one of the terminal oxygens that is bonded to the N. Don't forget that.

Regents: we had another brief quiz (to be graded soon, check website tomorrow). We reviewed metallic vs. ionic bonding and the physical properties associated with each: metals= good electrical conductors, malleable, high melting points; salts = poor electrical conductors (IN SOLID PHASE ONLY), brittle, and high melting points.
We then began our next MAJOR part of the course that requires practice and repetition to master: NAMING COMPOUNDS.
We talked about the rules for naming binary salts of representative and transition metals as well as salts of polyatomic ions (ternary salts). We finished with "hydrates". On Monday, we will learn how to name molecules and acids.

Honors: we went over the rest of the exceptions to the octet rule: Be and B molecular compounds. Remember, they CAN acquire an octet BUT you can draw legitimate Lewis structures of these Be and B molecular compounds with a quartet and a sextet of electrons, respectively. We also showed that, for compounds of elements in PERIODS 3 through 7, an "expanded octet" is possible and you WON'T have to guess when! Just follow the Lewis structure rules for single bonding to ALL terminal atoms and you will win.
We then began our next MAJOR part of the course that requires practice and repetition to master: NAMING COMPOUNDS.
We talked about the rules for naming binary salts of representative and transition metals as well as salts of polyatomic ions (ternary salts). On Monday, we will learn how to name hydrates, bases, molecules and acids. I will give you HUNDREDS of practice examples for hw until you know how to name any simple salt, base, molecule, acid and hydrate. Our test is next Tuesday and it will cover everything from the beginning of the Bonding Unit notes.
Monday, I will discuss the repeated failure to answer questions that were asked on your last test as well as the ignorance in following directions and the obvious lack of study (my definition of studying) and effort from MANY of you. Sadly, I can't force you to follow my directions and advice. If I could, everyone would be doing well. I can only clearly and explicitly show you and tell you what to do (see notes, worksheets, and complete explanations posted on the website as well as the mantras that I repeat in class) and hope that you follow the direction. Those who, for the sixth test in a row now, have ignored my advice and direction, once again wrote false, irrelevant, and/or incomplete answers or WASTED at least 10 to 15 minutes writing information that wasn't even asked for.

Honors: Lewis structures and more Lewis structures today. We learned about resonance structures which we draw and separate with double arrows. Resonance structures represent the sharing of certain valence electrons among several bonding nuclei throughout the molecule. Whenever you need to double bond or triple bond the central atom with one of several possible terminal atoms, you draw a resonance structure for each possible double or triple bonding pair of atoms.
We also drew structures for some polyatomic ions. Just keep in mind that Lewis structures for ANY ions, whether monatomic or polyatomic ions, ALWAYS get put in brackets with the magnitude of the charge FIRST and the sign of the charge NEXT outside the brackets. We also started to predict molecular and electronic geometry of a molecule or ion based on its Lewis structure. That will be the main consideration when we discuss molecular polarity.
By the way, some of you may not know the meaning of the word "polar". In covalent bonds, polar means that a partial negatively charged "pole" develops near the more electronegative atom and a partial positively charged "pole" develops near the less electronegative atom of the bonding atoms. So, just as the Earth (and our school) has a North "pole" and a South "pole", atoms that unequally share negative electrons develop opposite electrically charged "poles" at opposite ends of the bonding region.

Regents: we did some in-class review and learned about metallic bonding and how it accounts for:
1. the good electrical conductivity of metals due to the low Zeff on the valence electrons
2. the high melting point of metals due to the relatively strong metallic bonds due to the simultaneous attraction for all neighboring valence electrons among nearby metal atoms' nuclei. This multiple attraction creates strong bonding.
3. the malleability of metals; when you hammer the metal atom lattice, the mobile electrons just readjust their positions so that they are still between and attracted to multiple metal atoms' nuclei; the metal lattice doesn't break off.

We then contrasted a metal lattice with an ionic lattice of a salt. Salts are not malleable because when the lattice is hit with a hammer or mallet, the row or rows of ions will line up with like charges next to each other, which causes electronstatic repulsion which will make the row or rows of ions "break off' so the salt will crumble/be brittle. There will be a brief quiz tomorrow on ionic and molecular compounds, formulas, ionic charges, and Lewis structures. Our next full period exam will be given next Tuesday.

AP: we reviewed electronic and molecular geometry and related that to molecular polarity. We predicted intermolecular forces of attraction types based on molecular polarity. We reviewed delocalized bonding and counted the number of pi and sigma bonds in a given molecule or ion.
We started the seminal Molecular Orbital Theory. We STARTED it. Don't freak out if you don't get it yet. There isn't much to get! We haven't even gotten into the application of the theory! The practical questions that you will see are as easy if not EASIER than following the regular Aufbau principle in orbital diagrams of atoms. You'll see tomorrow as we go through the lesson using the new supercharged iBook!

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.

Honors: we reviewed the structure and formulas of binary ionic compounds (salts). We then discussed polyatomic ions and how to write formulas of ternary compounds, which are salts that are partially or completely made up of polyatomic ions. Do not forget the parentheses rule: e.g. Na2SO4 - no parentheses but Al2(SO4)3 must have parentheses because there is more than one of the polyatomic ions in the "formula unit".
We will cover covalent bonding tomorrow: covalently bond atoms generally form molecules, not "salts".

Regents: these quizzes are taking up some class time but I am seeing how few of you are taking the time to reinforce the class material by studying/re-writing the notes. Today's quiz, even with the advice given SECONDS before the exam resulted in unprecedented low grades (though some dramatically improved). It is absolutely unbelievable to me that, ten seconds after I warned the class to copy the polyatomic ions EXACTLY from the table, some students made the SAME EXACT mistakes that I explicitly warned them NOT to make; the resulting answers were totally wrong. There is no helping those who refuse to be helped. The irony is that, if you are reading this, you probably are doing fine because you care enough to check the site and review what we do in class.
Reminder: if you miss a quiz, the day that you return, you have to make up the quiz after school or you will receive a zero.

AP: we almost finished our elaborate molecular geometry/orbital hybridization chart. Try to write out the chart from scratch until you know all of the electronic and molecular geometries with the accompanying orbital hybridizations. Keep reviewing the videos, also. MOST of the next exam covers the aforementioned info.

AP: we further developed our all-encompassing chart with AX2E, AX4, AX3E, AX2E2, and AX5 structures. If you study the posted videos and look at the "floating" molecules that have always been just below the "Files" section of the class website, you will become familiar with all of these minimum repulsion electron geometries and the bond angles that result from the symmetric geometric distribution of electrons. Only the AX5 electron geometries result in two different bond angles. We will do more of those tomorrow.
Once the whole chart is done, we will do some more examples to make sure that everyone is solid gold on this ridiculously important and fun topic.

Honors: We determined how to tell from a chemical formula whether a compound is an ionically bonded salt or a covalently bonded molecule. We then focused on ionic bonding throughout a crystal lattice. In any salt lattice, each cation is completely surrounded by anions and vice versa BUT the ratio of cations to anions in the lattice overall is determined by the charges of the cations and anions. We showed how to determine the formula for any binary salt that contains the cations of a representative metal and anions of any nonmetal. We then showed the mechanism of electron transfer that would lead to the formation of the ions in the salt, which then ionically bond to each other due to the attractions of the oppositely charged ions. This bonding is tremendously potential energy lowering and, thus, stabilizing; that is why salts naturally form from metals and nonmetals and the process is quite exothermic. Tomorrow, we will continue with salt formulas and then we shall discuss covalent bonding (nonmetal to nonmetal!) in individual molecules.

Regents: we took our brief quiz and then we got into drawing Lewis Dot structures of molecules. There are four to five rules and they must be strictly obeyed IN ORDER, otherwise your structure will be flawed.
I finished grading the quiz from today. Some of you are still having trouble with this material yet extra help is a ghost town except for the students who are doing well who come to extra help (what a coincidence). If you are doing poorly and you can't/won't come to extra help, you're going to have to get a tutor NOW. This topic is never going to go away; it is intrinsic to the rest of the course.
Here are some of the problems that I witnessed from grading the quiz today:

1. Some students are using TWO CAPITAL LETTERS FOR ONE ELEMENT! This is UNBELIEVABLE! NOT ONLY have I NEVER drawn two capital letters for a single element, but also the Periodic Table CLEARLY shows the symbol for each element. For example, sodium (natrium) is Na, NOT NA !!!!!! Notice, EVERY SYMBOL THAT CONTAINS TWO LETTERS has ONLY THE FIRST LETTER IS CAPITALIZED! Do not "do your own thing" in chemistry. There are rules and conventions and, if you break them, then you are WRONG and you will NOT get credit. Chemistry rules are NOT ARBITRARY, they are VERY important. The rules were made to prevent ambiguity, confusion, and dangerous miscommunication.
Clearly, those who are making this error cannot be doing the homework or taking notes in class.

2. Reminder: you shouldn't need this crutch by now, however, the NAME and matching SYMBOL of EVERY ELEMENT ON THE PERIODIC TABLE is on reference table "S" !!! WHY did half of you use "B" for bromide??? Bromide is the anion of Bromine, which is Br, directly on Table S !!! "B" is Boron!

3. DO NOT DEVIATE IN ANY WAY, SHAPE, OR FORM from the polyatomic ions listed in Reference Table E!!! More than half of you wrote phosphate as Po4 3- instead of the WAY IT IS WRITTEN FOR YOU DIRECTLY IN THE TABLES; go check.
"Po" means Polonium, as you may have heard about in the news recently involving the killing of the Russian dissident.
The same goes for sulfate, which is NOT So4 2-; see and write the ion EXACTLY as it appears in Table E.

4. Here's a general EXTREMELY IMPORTANT TEST TAKING TIP, especially when the tests actually determine your average in the course: WRITE CLEARLY AND CAREFULLY!!! Test and quizzes are the main opportunity to show that you actually know the material.
Why did some students draw ALL FOUR LEWIS STRUCTURES in such a small space that the STRUCTURES OVERLAPPED??!!! That is absolutely unbelievable to me. I can't tell which electrons belong to which element!!! You therefore GET NOTHING. If you want credit, do not ever cram any answers together on any test.
You only had to take care and put more than ONE millimeter between your answers, not leave three quarters of the page BLANK! This is not a test of how much info that you can cram into a small space!

Follow the above advice TO THE LETTER on all upcoming tests and quizzes.

AP: Congratulations! You put in a great performance on the Bonding exam. The obvious care that went into most of your answers made the tests relatively easy to grade. Gilbert Lewis would be proud.
The average was an A, in the low to mid-90s percent-wise!
This test is a solid base for the next exam, too. We'll finish up our all encompassing electronic and molecular geometry chart early next week. When you can write out that chart on a whim (and you will), there will be big bucks for your tutoring entrepreneurship in college.
Keep up the great work!

Here are three links that will give you extra practice with getting the formula of an ionic compound and determining the formula of the compound from the name of the salt.
Writing Chemical Formulas

Naming Salts

Compound Names to Formulas

If you have questions, email me. Quiz Monday, Tuesday, etc.

There will be a quiz EVERY DAY next week on compound formulas, ionic charges, and Lewis dot structures and anything that we cover throughout the week. For each successive quiz, the time allowed will decrease. I warned you when I introduced this topic, you can take the time to practice and learn this now or you can eventually learn this after you lose hundreds of points due to your wanton ignorance. Formula naming and determination of ionic charge requires minimal thinking. It is just a procedure that ANY HUMAN can master with practice and repetition AND ALL of the answers ARE RIGHT ON THE PERIODIC/REFERENCE TABLE!!!
I can see that very few students in this class care or do any homework or studying. I get TWO TO THREE Regents students per WEEK at extra help! The class performance on this quiz shows that most of you should be at extra help EVERY DAY for at least an HOUR!
You will be quizzed daily until your behavior changes or you can plan to go to summer school which is GUARANTEED if these quiz results persist. If I see ANY flaking next week, detentions will be given out.

Happy extended weekend. The school looks awesome with all of the decorations so next week should be, as Borat says, "very nice". When we come back, we have six more full days of school; and then a li'l day of Christmas cheer, on which I gave a TEST last year, bah humbug! If we accomplish a lot next week, though, then there will not be a test on the day before our extremely long vacation into next year.

AP: I am going to try to video blog that last explanation since, as Josh figured out, I forgot to include among the orbitals the extra electron that makes nitrate an ANION! Actually, there is a subtle fact that needs to be seen in order for the explanation to make sense. The bottom line is that, though I want you to understand what is going on with orbital hybridization, the detailed explanation of the electrons rearrangement from atomic orbitals to hybrid orbitals is beyond the scope of the AP exam. Whatever is relevant, important, and practical, I will reiterate and give many more examples. The concept of "delocalized pi bonding" is important and, fortunately, is easy to explain and draw out.
This weekend, I hope to post the link to the video or, at least, to a written explanation/diagram.

Honors: We added a few ends to the Periodic Table unit such as naming the recently discovered d and p block heavy elements according to the IUPAC (international union of pure and applied chemists) nomenclature rules. We also talked about some chemical properties of fluorine.
We showed the formation of ionic bonds and compounds; we also learned how to draw the Lewis dot diagrams of atoms. These diagrams show the valence electrons around an atom; our diagrams are a little more sophisticated than those that you will find in many textbooks because we pair the first two electrons in the structure of each atom; that shows that the first two valence electrons are in the same "s" orbital.
I finished grading the Thanksgiving assignments and most of you did very well. It is disturbing, though, that a handful of you handed in HALF of the assignment (you weren't paying attention in class AND you do not read all of these posts). Some of you didn't follow directions and therefore missed credit on some questions. Worse, some of you cannot copy VERBATIM electron configurations out of a Reference Table or the textbook. That lack of effort, if it does not radically change, will kill your average for the quarter and beyond.

Regents: we had a brief quiz, which I reviewed for instant feedback.
Then, we talked mainly about covalent bonding, which is the sharing of electron pairs between two atoms (nuclei). There are two types of covalent bonds: polar and NONpolar. If the electrons are about equally shared, no electric poles develop, so the bond is nonpolar. If the electrons are NOT equally shared, a partial negative charge develops on the more electronegative atom and a partial positive charge develops on the less electronegative atom forming a POLAR covalent bond.
Regarding this, homework and worksheets will be posted tomorrow.

Regents: Chapters 9.1 and 9.2 in the text will give you some extra prep questions for tomorrow's quiz. The blue Barron's review book also has some questions on dot structures in the "Electronic Structure of Atoms" unit and questions about chemical formulas in sections 3.3 through 3.6.
I can't get to the website yet so I will post an extra set of questions on this blog:

1. What is the empirical formula of the following ionic compounds?
sodium sulfide, potassium phosphide, calcium perchlorate, aluminum phosphate, lithium fluoride

2. Write the charges of the cations and anions in the following compounds:
BaCl2 , CaS, CuCO3 , LiClO2

3. Draw the Lewis structures of the following atoms:
B, O, Ne, Al, Ar

answers to the above: (I don't have subscript fonts for this blog so the numbers are placed higher
or lower than they should be)

1. Na2S , K3P , Ca(ClO4)2 , AlPO4 , LiF ,

2. Ba 2+ , Cl - ; Ca 2+ , S 2- ; Cu 2+ , CO3 2- ; Li + , ClO2 - (all polyatomic ions that will be asked are on Table E of your Regents Reference Tables)

3. I can't draw structures on this blog but the dot structures for the first nineteen elements are posted here from the hw that you definitely did last week:
http://www.stanthonyshs.org/assignments/s4/113006txt7-1a.pdf

AP: Things looked good after a quick glance at the tests from today...I'll be grading them over the extended weekend.

Honors: You are welcome; yes, today's test was a gift in comparison to the tests from the past three years. If you had timing trouble, once again, you are not answering what is asked for. You have to constantly remind yourself that science writing does NOT require any fluff or extraneous information (unfortunately, filling out an essay with irrelevant prolix information tends to work well in grammar school); a lot of time is wasted writing true but irrelevant facts for which you will never earn a point.
You already knew exactly what was on the test. You just had to answer exactly and only what was asked for. I won't be writing this reminder again.
Today's performance (the degree to which directions were followed) will influence the quantity and style of questions on the next test.

Regents: we discussed polyatomic ions; the common ones are found on TABLE E in your review book. We then practiced writing formulas. Then, we came to the important practical point of relating ionic bonding in salts to their physical property of high melting points. Since ionic bonds are relatively strong, full electrostatic attractions between oppositely charged ions AND each ion in a salt crystal lattice is COMPLETELY SURROUNDED by , on average, SIX OR EIGHT oppositely charged ions (NO MATTER WHAT THE EMPIRICAL FORMULA OF THE SALT IS !!!) , there are MULTIPLE ionic bonds per each ion in any salt sample. Therefore, the ions are "frozen" in place next to each other in a solid salt sample. Relatively large amounts of energy are required to even BEGIN to get the ions to overcome their mutual attractions such that they can at least move over /"mosh with" each other while still remaining in contact. The large energy requirement is exhibited as a relatively HIGH melting point.

Then, another BIG point came up: Coulomb's Law is the reason for different degrees of attraction between differently charged ions that are at different average distances from each other in a lattice. From our last unit, Coulomb's Law is also THE REASON that high Zeff nuclei attract valence electrons stronger than do low Zeff nuclei, so I expected you to know this already.
Bottom line: the higher the charge on the oppositely charged ions, the greater the strength of the ionic bond. Coulomb's Law states that the higher the product of the magnitudes/sizes of the oppositely charged particles, the stronger the force of attraction. Coulomb also states that, the CLOSER that the oppositely charged particles are to each other, the STRONGER the electrostatic force of attraction. This law/observation GOVERNS/RULES all of chemistry!
So, the higher the charges of the cations and anions AND the smaller they are (fewer OPEL's) the stronger the ionic bonds.
For example, NaCl has positive and negative one charged ions, respectively. AlN has positive and negative THREE charged ions! Therefore, the ionic bonds among the Al 3+ and the N 3- ions are much stronger than the ionic bonds among the Na + and Cl - ions. That is why the melting point of aluminum nitride is MUCH HIGHER than the melting point of sodium chloride.
The distances among the ions are not that different (same #'s of OPEL'S) in this case so that is not a significant factor towards the different melting points.
End of story.
Tomorrow there will be a BRIEF quiz. I HIGHLY recommend that you know the symbols of the first 36 elements by now so that you do not have to slow down and look them up. I also recommend that you know all of the halogens and the Group I and Group 2 metal symbols by heart. Know compound formulas, charges of ions, and Lewis dot structures for ATOMS. If the class does not come in prepared, we will have a quiz EVERY DAY FOR THE REST OF THE QUARTER.

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.

Honors: we just about finished the Periodic Table Unit. Notes for our new unit, the heart of chemistry, the all-important "Chemical Bonding" unit, will be posted tonight.
Note: in the Orange Review Book, questions regarding the formulas of compounds and oxidation states won't be covered or tested on Wednesday's test.
Note 2: this is a GOOD one: thanks to our Marisa for bringing up, at extra help, a question from the last multiple choice test. As we discussed the answers, it became apparent that two of the answers were possible or at least arguably close calls. Bring in your tests tomorrow and I will check whether you have one of the two correct answers. The class average is going up! Good times.
It also became apparent how many students had misgrids on this test. Up to this test, I have allowed misgrids to be corrected but that will not be the case on tests for at least the near future. I aim to discourage careless gridding so you are going to eat the lost points, if you misgrid on upcoming tests.

The end of the Periodic Table consists of physical and chemical characteristics of the various groups of elements. Memorization is key; any of these minute but practical facts can and will be tested on the Regents and SAT II exams.
In the review book hw from this past weekend, there is some information about oxidation numbers and compound formulas. Don't worry about those things for now. We will cover them in the next unit.

Regents: we calculated the empirical formulas of many salts and then we reversed the process and went from the name of the compound to what must be the empirical formula of the compound. We also did test review.
Tomorrow, we will start with the empirical formula of a compound, predict the name, and find the charge on the respective cation and anion.

AP: we did examples of structures that had various bond orders and bond lengths. As bond order increases, bond strength increases BUT bond length decreases. The more pairs of electrons that are shared between two positive nuclei, the greater the NET force of attraction between the two bonded atoms, thus the shorter the bond length.
We further practiced resonance structures and calculated bond order by dividing the total number of bonds between the different atoms by the number of "bonding regions/domains" between the different atoms.
We explained the phenomenon of "smog" on a warm day and clear yet polluted skies on a cool day by showing the dimerization of nitrogen dioxide to dinitrogen tetroxide. We discussed Le Chatelier's Principle and the thermodynamics of bond formation (exothermic) and bond breakage (endothermic) and related the rates of the forward and reverse reactions to increasing or decreasing temperatures.
Tomorrow, we cover the last material before our next test. This extended weekend, we will cover the transition metal complex topic in the text. You will quickly become expert at naming transition metal complexes and the reactions that form them.

...will cover ALL notes on the Periodic table. The test is on Wednesday. AP also has their test on Wednesday.
We have four days of school this week, five days next week, and about one day the following week and that's all for 2006.
There is little time this quarter so don't fall behind and be thoroughly prepared for our few remaining tests this quarter (there won't be many due to all of the vacation and probably some snow days).

...were not abominable but they were relatively weak. On the Quantum and the Periodic Table Unit, I haven't had an Honors class with a multiple choice test average under a 90 in over two years! This test consisted of REGENTS questions! ALL of the questions were EXPLICITLY covered in the notes, hw, and practice tests. SOME of the questions were VERBATIM from those sources. That means that some students, UNBELIEVABLY, are still trying to get away with not doing as much as they need to in this class. I can clearly and plainly see who is practicing, doing the hw, taking good notes, and following good test-taking advice based on what is written and NOT written on your tests. The UNBELIEVABLY low percentage of students who come in to correct their past tests, no matter how low the grade, is sad and appalling. Good for those who do try to improve themselves, though. Speaking of which, on Monday, bring in your last written exam. I have a few points to make regarding that test so that I do not see the same errors on the next test.

You already know that: 1. This class is harder and 2. Chemistry requires more knowledge than other subjects do. You need to step up your game by studying=writing more, focusing more in class, taking better notes, and coming to extra help. You should try to make as many mistakes as possible BEFORE each test so that you can correct your misconceptions and poor test-taking skills BEFORE each test. Stop making excuses and come prepared with questions, seriously. I've been at extra help for three hours per day since September. Most days, the same three good students are there and, the DAY before a test, the number attending mushrooms to about 15.

Careless errors, not drawing out models or pictures, and answering the OPPOSITE of what the questions asked for were the most common mistakes. There were NO hundreds. There were enough high 90's to balance out the low 70's for the resulting averages:

D Period: 86
G Period: 84

The written response test on Wednesday will be significantly more challenging than any multiple choice test due to the challenge of writing cogent, logical, and thorough explanations, so you should prepare much more for that test. Best to come to extra help.

Good times at the Christmas Concert last night. If you missed the show, you should check it out tonight. It's like an early Christmas gift.

AP: we covered the "electron-deficient" species of Be (relatively stable with 4 valence electrons) and B (relatively stable with 6 valence electrons), which we will see again when we do Lewis Acids (electron pair ACCEPTORS=ACIDS). We also covered some compounds in which we are forced to expand the octet around the CENTRAL atom i.e. SF6, IBr5, SF4.... and we finished up our talk on "formal charge" emphasizing the MAGNITUDES , NOT THE SIGNS, of the formal charges in order to determine the most significantly contributing resonance structure....ONLY IF there is a tie between/among structures do we invoke/use rule 2: the structure with the negative charge on the more/most electronegative atom is more significant.
This class is on point even with our tight schedule (thanks to minimal disruption from a certain courtyard during certain periods!). Keep up the good focus and we will be even better prepared for the topics ahead.
Your lengthy written responses on the last test were pretty good although you will see that errors in logic, CLARITY, spelling, and grammar cost you some points here and there. There were also some laziness points lost due to unsupported Zeff and OPEL contentions and some nice drawings that were NEVER USED OR REFERRED TO!

Regents: we further practiced our ionically bonded salt formulas and some even saw a shortcut that I will NOT BE TEACHING due to the damage done/errors/points lost from its misuse and inconsistent use. ITS NOT EVEN much of a shortcut. Using it, you might save a second on a GOOD day.
Bring in the tests that I gave back on Friday. We will go over select questions on Monday.

Honors: you took the multiple choice version of your Quantum/Periodic Table exam. From what I saw, a lot of students UNNECESSARILY RUSHED through the test and ignored good test-taking practices such as READING EACH QUESTION CAREFULLY AND DRAWING OUT A COMPLETE PREDICTED ANSWERS. This ignorance (in the true sense of the word, "to ignore") cost a lot of students a lot of points! It's getting pretty late in the game to still refuse to properly employ good test-taking advice. How many more careless errors are you going to have to make before you are more careful? Because every performance counts in this class, you should be motivated to improve earnestly your test-taking skills.