<p>How can you tell if compounds are polar ??? For example..</p>
<p>TeCl2
PH3
AsCl5
RnF4
IBr4 -1
?? Thanks</p>
<p>Draw out the Lewis Structures for them and see if the compounds are symmetrical.
Also look at electronegativity differences.</p>
<p>That's about right. More specifically, if electronegativity differences between two atoms are, if I remember correctly, about 0.4 < x < 2.0, the BOND is polar. Below 0.4 is nonpolar, and 2.0+ is ionic. If I remember correctly. After you determine bond polarity, you can look at molecule polarity, and that depends on the shape.</p>
<p>In terms of structure, while bonds might be polar, the molecule may not necessarily be polar. For example, many tetrahedral molecules with polar bonds and formulas AB4 are usually nonpolar because the vectors indicating polarity will cancel each other out. (And example of this is CCl4. While the electronegativity difference between C and Cl is ~0.5 (indicating a polar bond), the molecule itself is nonpolar).</p>
<p>Water, H2O, is polar because 1) The H-O bond is polar, and then 2) the polar bond vectors add up so that the "O" side of the molecule is slightly negative, and the "H" is slightly positive.</p>
<p>Hopefully that made sense? I'm not the best teacher.</p>
<p>With regards to the scale for electronegativity difference. I learned it was < 0.3 was nonpolar, 0.3 < x < 1.7 - polar, and > 1.7 is ionic.</p>
<p>I guess arguments can be made there depending on the textbook used.</p>
<p>Yeah, that would probably account for it. Though the AP Chem book we used to use was riddled with mistakes, because apparently the authors had grad students writing answers to the problems. My Chem teacher had us cross out the electron affinity section because it was literally just plain wrong. Apparently the school district is going to buy the updated version for next year, so that means free chem textbook book for me :)</p>
<p>hehe</p>
<p>What textbook are you using for AP Chem?</p>
<p>We're using Silberberg 5th Edition, but I have a copy of Zuhmdahl that I plan on looking at. </p>
<p>We are on Equilibrium and LeChatelier's Principle.</p>
<p>Zumdahl's def. the best for ap chem!!</p>
<p>Im still really confused :-/ can someone tell me what they think the above compounds are?</p>
<p>It seems to me that you want us to do the work for you.</p>
<p>Based on your previous posts, you don't fully understand the concepts being taught in class. I suggest reading the chapter on Molecular Shapes and Molecular Polarities and follow some of the examples in the book. If you are really struggling, talk to your teacher. </p>
<p>This type of concept should not be too difficult if you are reading the book, taking notes, and making connections between different concepts.</p>
<p>I'll start you off with TeCl2.</p>
<p>Te has 6 valence electrons, so it has two bond sites, one for each Chlorine to attach to.
If you draw out the Lewis Structure for it, you see that the structure is symmetrical with polarity pointing towards both chlorines. This tells you it is nonpolar.</p>
<p>I'm told Zumdahl is pretty good. We use Kotz & Treichel's 5th ed. It's a pretty good book, but the solutions are often off/disregard significant digits.</p>
<p>zumdahl's what we're using in my intro chem class at penn :) great book!</p>
<p>I have no idea what any of you are talking about and I got a 3 on the AP test last year...huzzah for random guessing!</p>
<p>yah we used zumdahl too, i got a 4 but most of the people that took it with me got 5's ..grrr</p>
<p>How hard is the AP Chem class? I know it varies, but is it extremely difficult?</p>
<p>Nope, just got to put your effort into it.</p>
<p>IBr4 1-</p>
<p>I was thinking about this one... do you assume the central Iodine octet expands to 12? And if so... nonpolar, right?</p>
<p>We use Raymond Chang's book. It is pretty solid, do any of you use/have used it before? Also, AP chem is difficult...but manageable if you do the work and all the extra exercises/practice problems. I had too many things last semester going on so I wasn't able to devote myself fully, but I still ended up getting decent grades. It's definitely a class you can work hard in and get rewarded. Some classes...you just know it or you don't.</p>
<p>Um...just a note...polarity doesn't really have anything to do with symmetry. Plenty of symmetrical compounds are nonpolar, and plenty of polar compounds are nonsymmetrical.</p>