Search found 30 matches
- Tue Jun 12, 2018 12:52 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 2999123
Re: Post All Chemistry Jokes Here
The optimist sees the glass half full. The pessimist sees the glass half empty. The chemist sees the glass completely full, half with liquid and half with air.
- Tue Jun 12, 2018 12:48 pm
- Forum: General Science Questions
- Topic: Bond angles
- Replies: 4
- Views: 830
Re: Bond angles
The VSEPR formula really helps with determining the shape and bond angles!
- Sat Jun 02, 2018 4:54 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: regions of e- density
- Replies: 4
- Views: 480
Re: regions of e- density
in addition, multiple bonds are treated as equal to single bonds; i.e. a double bond does not have more repulsion than a single bond.
- Sat Jun 02, 2018 4:33 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bond Angles
- Replies: 7
- Views: 810
Re: Bond Angles
It would also be helpful to consider the repulsion between lone pairs and bonds. With the Lewis structure and the shape known, you can use lone-lone > lone-bond > bond-bond to help with determining bond angle.
- Sat Jun 02, 2018 4:27 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Lone Pairs
- Replies: 2
- Views: 320
Re: Lone Pairs
To add on, the lone pairs will push away from the bonds stronger, making bond angles smaller. Thus, looking at the VSEPR formula is extremely helpful when determining shape. For example, AX3 will yield trigonal planar with bond angles 109.5 but AX3E will yield trigonal pyramidal with bond angles <10...
- Sun May 27, 2018 12:17 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 2999123
Re: Post All Chemistry Jokes Here
*texting a chemistry major*
"Hey you wanna go to the movies rn?"
"Sure, when?"
"Rn"
"What do you mean by Radon?"
"..."
"Hey you wanna go to the movies rn?"
"Sure, when?"
"Rn"
"What do you mean by Radon?"
"..."
- Sun May 27, 2018 12:02 pm
- Forum: Ionic & Covalent Bonds
- Topic: Group 17
- Replies: 2
- Views: 443
Re: Group 17
To expand, the elements under Flourine in group 17 are all exceptions to the octet rule.
- Sun May 27, 2018 11:56 am
- Forum: Electronegativity
- Topic: Calculating electronegativity
- Replies: 10
- Views: 1252
Re: Calculating electronegativity
When comparing electronegativity between elements, you can assume that the element that has more valence electrons or a fuller outer shell is more electronegative.
- Sun May 20, 2018 2:53 pm
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: Polarizability
- Replies: 7
- Views: 677
Re: Polarizability
Yes, exactly :)
- Sun May 20, 2018 2:50 pm
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: Polarizability
- Replies: 7
- Views: 677
Re: Polarizability
Anions are opposite from anions; polarizability increases as ions get larger and less electronegative.
- Sun May 20, 2018 2:49 pm
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: Polarizability
- Replies: 7
- Views: 677
Re: Polarizability
Smaller, more highly-charged cations have greater polarization power. In terms of ionic radius, polarization increases from big to small atoms. You can refer to question 3.81.
- Sun May 20, 2018 2:47 pm
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: Polarizability
- Replies: 7
- Views: 677
Re: Polarizability
Generally, larger molecules are more polarizable than smaller molecules.
- Tue May 15, 2018 11:24 pm
- Forum: Lewis Structures
- Topic: Identifying elements in Lewis structures [ENDORSED]
- Replies: 2
- Views: 722
Re: Identifying elements in Lewis structures [ENDORSED]
Lavelle hasn't gone over this so I'm not 100% certain, but I would use the charges of the known elements in the lewis structure, count the number of shared electrons/bonds the central element has, and count the total number of electrons the lewis structure contains. I think all of these would help s...
- Tue May 15, 2018 11:12 pm
- Forum: Ionic & Covalent Bonds
- Topic: Name to Bond [ENDORSED]
- Replies: 1
- Views: 306
Re: Name to Bond [ENDORSED]
I think the numbers represent the charge of the element. For example, CuO can be written as Copper(II) oxide to describe that copper has a +2 charge. Since O has a -2 charge, the overall charge is 0. For thallium III chloride: Tl has a +3 charge and Cl has a -1 charge, so you need 3 Cl to make the c...
- Tue May 15, 2018 11:02 pm
- Forum: Lewis Structures
- Topic: Which atom to have the charge in lewis structures
- Replies: 2
- Views: 399
Re: Which atom to have the charge in lewis structures
I believe that the charge should be on whatever atom has the extra/remaining (whether it be positive or negative) charge. For example, during lecture on Friday, one of the TA's wrote the lewis structure of SO4-2 with 4 single bonds (all the O's had -1 charge and the S had a +2 charge). After rewriti...
- Sun May 06, 2018 1:24 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Unpaired Electrons from Electron Configurations [ENDORSED]
- Replies: 2
- Views: 1224
Unpaired Electrons from Electron Configurations [ENDORSED]
How do you determine the number of unpaired electrons if you are given the electron configuration of an element?
- Sun May 06, 2018 1:14 pm
- Forum: Trends in The Periodic Table
- Topic: Isoelectric Atomic Radii
- Replies: 3
- Views: 369
Re: Isoelectric Atomic Radii
Just to elaborate on the trend, atomic radii increases as you go down and to the left of the periodic table. For example, look at homework #2.59
- Sun Apr 29, 2018 2:11 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Electrons in an Orbital [ENDORSED]
- Replies: 8
- Views: 833
Re: Electrons in an Orbital [ENDORSED]
For instance, in the carbon example that Lavelle gave us in class, why are the two electrons in two different orbitals even though they are in the same subshell? Is it just because they have the same spin?
- Sun Apr 29, 2018 2:01 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Electrons in an Orbital [ENDORSED]
- Replies: 8
- Views: 833
Re: Electrons in an Orbital [ENDORSED]
And just to confirm, those two electrons need to have opposite spins, otherwise they cannot be together?
- Sun Apr 29, 2018 1:56 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Electrons in an Orbital [ENDORSED]
- Replies: 8
- Views: 833
Electrons in an Orbital [ENDORSED]
Hi, I wasn't able to come to lecture on Friday, so I'm unsure about the number of electrons in a orbital. I've seen models where there are up to 8 electrons in an orbital, is the maximum really just two?
- Sun Apr 22, 2018 6:50 pm
- Forum: Photoelectric Effect
- Topic: Wave vs. Particle
- Replies: 8
- Views: 663
Re: Wave vs. Particle
sorry, correction: the wave model is on wavelength and frequency* (not amplitude)
- Sun Apr 22, 2018 1:04 pm
- Forum: Photoelectric Effect
- Topic: Wave vs. Particle
- Replies: 8
- Views: 663
Re: Wave vs. Particle
Yes, exactly :)
- Sun Apr 22, 2018 1:01 pm
- Forum: Photoelectric Effect
- Topic: Wave vs. Particle
- Replies: 8
- Views: 663
Re: Wave vs. Particle
If you increase the intensity of the wave, it just increases the number of photons that are being directed at the piece of metal, thus increasing the number of electrons being ejected (1:1 photon electron ratio). However, if the wavelength (aka the energy of the photon) is not enough to eject an ele...
- Sun Apr 22, 2018 12:56 pm
- Forum: Photoelectric Effect
- Topic: Wave vs. Particle
- Replies: 8
- Views: 663
Re: Wave vs. Particle
The wave model for light is in regards to wavelength and amplitude (aka intensity). When you look at the light model in regards to particles, you look at the photon energies of the light.
- Wed Apr 11, 2018 11:05 am
- Forum: Molarity, Solutions, Dilutions
- Topic: STEPS to figuring out solutions/ molarity quesitons
- Replies: 2
- Views: 343
Re: STEPS to figuring out solutions/ molarity quesitons
Mainly, I think the main topics would be find the molarity, find the concentration of ions, molecules, etc.
- Wed Apr 11, 2018 10:51 am
- Forum: Properties of Light
- Topic: Value of Speed of Light** (Shoutout to Dr. Lavelle for calling me out in lecture today) [ENDORSED]
- Replies: 4
- Views: 552
Re: Value of Speed of Life [ENDORSED]
I think it's preferred to use the scientific notation for the speed of light when making calculations. It's 3.00*10^8m/s
- Wed Apr 11, 2018 10:46 am
- Forum: SI Units, Unit Conversions
- Topic: Formula Units
- Replies: 5
- Views: 885
Re: Formula Units
So for covalent bonds, you would answer with something like 6.022*10^23 molecules, and then for ionic bonds, you would answer with 6.022*10^23 formula units?
- Wed Apr 11, 2018 10:41 am
- Forum: SI Units, Unit Conversions
- Topic: Formula Units
- Replies: 5
- Views: 885
Re: Formula Units
So in e21, it says to calculate moles and the number of molecules and formula units/atoms in a) 10.0 g of alumina Al2O3. I know how to convert that to moles, since you just divide by the molar mass of alumina, and for the number of molecules, you multiply the number of moles by Avogadro's number. Bu...
- Wed Apr 11, 2018 10:32 am
- Forum: SI Units, Unit Conversions
- Topic: Formula Units
- Replies: 5
- Views: 885
Formula Units
In practice problem E25, it asks about the number of formula units in 0.750 mol KNO3. What are formula units?
- Wed Apr 11, 2018 10:28 am
- Forum: SI Units, Unit Conversions
- Topic: Length Units
- Replies: 15
- Views: 1454
Re: Length Units
Yeah, I think that we do automatically infer that we answer in SI units since he went over SI units in lecture and since they apply to scientific notation.