Search found 31 matches
- Mon Jun 04, 2018 10:09 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: 17.33 - Polydentate ligands
- Replies: 1
- Views: 167
17.33 - Polydentate ligands
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. ...
- Mon Jun 04, 2018 12:37 pm
- Forum: Bond Lengths & Energies
- Topic: Ionic Character
- Replies: 12
- Views: 3389
Re: Ionic Character
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...
- Mon Jun 04, 2018 12:25 pm
- Forum: Hybridization
- Topic: Question 4.25 Part A
- Replies: 2
- Views: 164
Re: Question 4.25 Part A
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.
- Fri Jun 01, 2018 12:57 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: 4.25 a
- Replies: 2
- Views: 200
Re: 4.25 a
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...
- Tue May 29, 2018 10:47 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Cancelling out dipole moments
- Replies: 3
- Views: 494
Re: Cancelling out dipole moments
If they are opposite of each other (180˚) then they cancel. If they are anything less than 180˚, they do not cancel.
- Thu May 24, 2018 11:17 am
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: Polarity
- Replies: 2
- Views: 298
Re: Polarity
"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." ...
- Thu May 24, 2018 11:15 am
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: Polarizing power vs polarizability
- Replies: 2
- Views: 316
Re: Polarizing power vs polarizability
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...
- Tue May 22, 2018 10:08 pm
- Forum: Electronegativity
- Topic: Trends? [ENDORSED]
- Replies: 10
- Views: 940
Re: Trends? [ENDORSED]
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.
- Tue May 22, 2018 10:00 pm
- Forum: Lewis Structures
- Topic: lowest energy & most stable Lewis structures
- Replies: 4
- Views: 1259
Re: lowest energy & most stable Lewis structures
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, ...
- Tue May 22, 2018 9:56 pm
- Forum: Lewis Structures
- Topic: Lewis Structure tips?
- Replies: 2
- Views: 232
Re: Lewis Structure tips?
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,...
- Fri May 18, 2018 5:20 pm
- Forum: Lewis Structures
- Topic: Naming compounds
- Replies: 3
- Views: 263
Re: Naming compounds
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!
- Thu May 17, 2018 1:54 pm
- Forum: Coordinate Covalent Bonds
- Topic: Coordinate Covalent Bonds
- Replies: 4
- Views: 592
Re: Coordinate Covalent Bonds
Coordinate covalent bonds are where both of the electrons that form the bond originate from the same atom.
- Thu May 17, 2018 1:47 pm
- Forum: Lewis Structures
- Topic: Finding a Lewis Structure with the Lowest Energy
- Replies: 5
- Views: 336
Re: Finding a Lewis Structure with the Lowest Energy
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.
- Thu May 17, 2018 1:21 pm
- Forum: Trends in The Periodic Table
- Topic: Electron Repulsion and Trends
- Replies: 1
- Views: 468
Re: Electron Repulsion and Trends
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...
- Thu May 10, 2018 12:32 pm
- Forum: Octet Exceptions
- Topic: Octet exceptions and Formal charges.
- Replies: 6
- Views: 557
Re: Octet exceptions and Formal charges.
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.
- Sun May 06, 2018 12:18 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Importance of Nodal Planes
- Replies: 1
- Views: 194
Importance of Nodal Planes
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?
- Sun May 06, 2018 12:09 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Switching 3d and 4s
- Replies: 6
- Views: 539
Re: Switching 3d and 4s
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...
- Sun May 06, 2018 12:01 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Configuration of Fe
- Replies: 2
- Views: 216
Re: Configuration of Fe
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.
- Tue Apr 24, 2018 11:04 pm
- Forum: Einstein Equation
- Topic: converting from keV to joules
- Replies: 7
- Views: 473
Re: converting from keV to joules
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.
- Tue Apr 24, 2018 11:02 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Rydberg [ENDORSED]
- Replies: 4
- Views: 281
Re: Rydberg [ENDORSED]
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...
- Tue Apr 24, 2018 11:00 pm
- Forum: Properties of Electrons
- Topic: Information Provided on Exam
- Replies: 6
- Views: 447
Re: Information Provided on Exam
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.
- Wed Apr 18, 2018 1:28 pm
- Forum: Properties of Light
- Topic: The speed of light
- Replies: 4
- Views: 252
Re: The speed of light
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"?
- Wed Apr 18, 2018 1:25 pm
- Forum: Properties of Light
- Topic: Question 1.11
- Replies: 2
- Views: 216
Re: Question 1.11
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...
- Wed Apr 18, 2018 1:19 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Wave and Particle Properties of Electrons and Photons
- Replies: 1
- Views: 82
Re: Wave and Particle Properties of Electrons and Photons
An electron is a particle. Light, however, has properties of both waves and particles, which is what the experiments we reviewed in class proved.
- Sun Apr 15, 2018 6:06 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Homework 1.13 [ENDORSED]
- Replies: 3
- Views: 266
Re: Homework 1.13 [ENDORSED]
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.
- Thu Apr 12, 2018 5:33 pm
- Forum: Molarity, Solutions, Dilutions
- Topic: Units - L or mL? [ENDORSED]
- Replies: 15
- Views: 1441
Re: Units - L or mL? [ENDORSED]
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.
- Thu Apr 12, 2018 5:26 pm
- Forum: SI Units, Unit Conversions
- Topic: Correct Units?? [ENDORSED]
- Replies: 8
- Views: 524
Re: Correct Units?? [ENDORSED]
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.
- Thu Apr 12, 2018 5:21 pm
- Forum: Significant Figures
- Topic: Sig fig simple question [ENDORSED]
- Replies: 5
- Views: 334
Re: Sig fig simple question [ENDORSED]
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.
- Mon Apr 09, 2018 12:01 am
- Forum: SI Units, Unit Conversions
- Topic: SI units [ENDORSED]
- Replies: 6
- Views: 573
Re: SI units [ENDORSED]
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.
- Sun Apr 08, 2018 11:59 pm
- Forum: Balancing Chemical Reactions
- Topic: Another Way to Balance
- Replies: 7
- Views: 509
Another Way to Balance
Is there another way to balance equations that doesn't involve just "guess and check"? Maybe something that is more systematic?
- Sun Apr 08, 2018 11:57 pm
- Forum: Significant Figures
- Topic: Basic Sig Figs
- Replies: 13
- Views: 1315
Re: Basic Sig Figs
Is maintaining significant figures necessary in this class? I can't remember if he mentioned it. If so, I would need a refresher..