CHEMISTRY COMMUNITY

kendallbottrell

I have noticed that when determining if a molecule is polydentate or not, atoms that are attached to the central atom by double bonds do not "count" as ligands. For example, C204 2-, is bidentate even though it has four attached oxygen atoms because two of them are bonded by double bonds. ...

kendallbottrell

Ionic character is determined in terms of "greater ionic character" and "lower ionic character". If a molecule has increasing or a higher difference in electronegativities, then there is a greater ionic character. If the difference in electronegativity is decreasing (becoming mor...

kendallbottrell

You have to figure out the 3-D structure and picture it to realize the orientation of the Cl atoms. Even if you do put them opposite of each other on the Lewis structure, on the VSEPR model, the Cl atoms would not be opposite of each other, and therefore not cancel.

kendallbottrell

When you're doing polar/nonpolar problems, it is important to think of the 3D model/shape because you could see that no matter where you put the H or Cl, dipole moments will not cancel each other. If you only look at the Lewis structure, then you can get confused because it would look like they woul...

kendallbottrell

If they are opposite of each other (180˚) then they cancel. If they are anything less than 180˚, they do not cancel.

kendallbottrell

"Something that is highly polarizable means that it is susceptible to being distorted causing a dipole to form. A larger atom is more polarizable than a smaller one because its outer electrons are less tightly bound and its electron cloud is more likely to be distorted by, say, a cation." ...

kendallbottrell

Polarizing power is the ability to distort electron clouds and polarizability to the extent to which an electron cloud is distorted. Cations have polarizing power because the small atoms with positive charge attract and distort the electrons of an anion. Anions are polarizable because their electron...

kendallbottrell

Jordanmarshall wrote:So why is Oxygen more electronegative than Chlorine?

The simple answer is that going across the periodic table has a less significant impact on electronegativity than going down it does.

kendallbottrell

To choose the most stable Lewis structure with the lowest energy, calculate the formal charges for all the atoms and choose the molecule that has all of them closest to zero. This ties into resonance structures - for example, if you have charges on one form of -2, +1, -1 and on another form 0,+1,0, ...

kendallbottrell

For larger organic molecules (with lots of C,H,O,N) a TA suggested doing the Lewis structure and leaving the hydrogens off at first, then calculating the formal charge, and then adding the H atoms where they are needed to neutralize the formal charges. This was very efficient and it helped me a lot,...

kendallbottrell

A couple TA's have suggested memorizing common polyatomic ions, not for the test/exams but just for the future! They are really helpful with naming!

kendallbottrell

Coordinate covalent bonds are where both of the electrons that form the bond originate from the same atom.

kendallbottrell

Typically I bond the elements together and then distribute the electrons and then calculate the formal charges. If the formal charges are not close enough to zero, I redistribute some electrons between the elements in the form of bonds (double, triple, etc). And then recalculate the formal charges.

kendallbottrell

The more electrons there are, the stronger the electron repulsion. A larger cloud and more electrons would mean that the electron repulsion is high and for those atoms, it would be easier to lose the electrons, especially in the outer shells. This means that the elements with larger atomic radii als...

kendallbottrell

A lot of time you can use the idea of symmetry when doing bonding questions, but just to make sure you're actually correct, it is important to do the formal charge calculations. From there you would be able to tell if the structures have resonances easier too.

kendallbottrell

Why are nodal planes important to know? What information do they provide us? Would understanding the shapes help us understand energy levels or orbitals at all?

kendallbottrell

3d actually does not have a higher energy than 4s, which is why it must be placed before 4s and 4p when writing out the electron configurations. If you follow the pattern across the periodic table, you will be able to see the corresponding energy levels. There is 3s and 3p before 3d, so that means t...

kendallbottrell

Remember that it is very likely you will be able to use the "shorthand" - [Ar] 3d^6 4s^2. If it helps, a TA suggested writing it out the way you see it and then rearranging the the d orbital before the s orbital.

kendallbottrell

You do not have to memorize that! The conversion of eV to J is given, and as for the k part, you would just use the conversion of (1000J / 1kJ) - because of the prefix kilo.

kendallbottrell

Just the energy difference by itself can be stated as a negative number because, like you said, it just shows that light was being emitted. However, if you want to find the wavelength, you need to omit the negative signs because there is no such thing as a negative wavelength - same thing goes for f...

kendallbottrell

As far as I know, you will not be provided the wavelengths, so you should know the general ranges. You most likely will not need to know the specific colors of visible light, like red or green. Also, it may be helpful to know the spectrum in order of lowest to highest frequency.

kendallbottrell

Luis Avalos 1D wrote:In a vacuum, yes. The only thing that's different is their frequencies & wavelengths I believe.

What does it necessarily mean when one says "in a vacuum"?

kendallbottrell

The lower energy level in this context is referring to the level that each series starts at. UV light corresponds to n=1, visible light corresponds to n=2, and infrared light corresponds to n=3. When you do problems with the different series, when they say "lower energy level", you must as...

kendallbottrell

An electron is a particle. Light, however, has properties of both waves and particles, which is what the experiments we reviewed in class proved.

kendallbottrell

Also, the question should have specified which one was n1 and which was n2, so don't get confused! It is supposed to be { 1/4 - 1/16}, not the other way around.

kendallbottrell

When you're using the conc=moles/vol, you need to use liters. But when you you're using the M1V1=M2V2 equation, you just need to keep all of the units the same, so essentially you can use mL instead of L.

kendallbottrell

A good rule of thumb is following the units the problem gives when stating the initial amounts. If they are initially given in kg, then they typically expect your answer to also be in kg.

kendallbottrell

Yes, when multiplying and dividing in a problem, you round to the least number of significant figures in the problem. In addition and subtraction, you round to the least number of decimals in the problem.

kendallbottrell

There are charts in the back of the book that will help with memorizing important conversions. That is where you will find the most commonly used ones in problems.

kendallbottrell

Is there another way to balance equations that doesn't involve just "guess and check"? Maybe something that is more systematic?

kendallbottrell

Is maintaining significant figures necessary in this class? I can't remember if he mentioned it. If so, I would need a refresher..

CHEMISTRY COMMUNITY

Search found 31 matches

17.33 - Polydentate ligands

Re: Ionic Character

Re: Question 4.25 Part A

Re: 4.25 a

Re: Cancelling out dipole moments

Re: Polarity

Re: Polarizing power vs polarizability

Re: Trends? [ENDORSED]

Re: lowest energy & most stable Lewis structures

Re: Lewis Structure tips?

Re: Naming compounds

Re: Coordinate Covalent Bonds

Re: Finding a Lewis Structure with the Lowest Energy

Re: Electron Repulsion and Trends

Re: Octet exceptions and Formal charges.

Importance of Nodal Planes

Re: Switching 3d and 4s

Re: Configuration of Fe

Re: converting from keV to joules

Re: Rydberg [ENDORSED]

Re: Information Provided on Exam

Re: The speed of light

Re: Question 1.11

Re: Wave and Particle Properties of Electrons and Photons

Re: Homework 1.13 [ENDORSED]

Re: Units - L or mL? [ENDORSED]

Re: Correct Units?? [ENDORSED]

Re: Sig fig simple question [ENDORSED]

Re: SI units [ENDORSED]

Another Way to Balance

Re: Basic Sig Figs