## Search found 32 matches

Tue Jun 05, 2018 1:16 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: HW 4.19
Replies: 3
Views: 343

### Re: HW 4.19

With bigger molecules like this one, it will often be asked what the shape is surrounding an individual atom such as one of the Carbons in the atom. In this case you would say tetrahedral because there are 4 atoms around the central atom with no lone pairs.
Tue Jun 05, 2018 1:13 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR
Replies: 7
Views: 456

### Re: VSEPR

Personally I have found the most success in determining shape through the VSEPR formula. I have associated each individual formula with its corresponding shape, so if you learn similarly then I would suggest this.
Tue Jun 05, 2018 1:08 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Trigonal Planar vs Trigonal Pyramidal
Replies: 5
Views: 10451

### Re: Trigonal Planar vs Trigonal Pyramidal

The bond angles are also different for the two molecules. For trigonal planar, the bond angles are all 120 degrees while in trigonal pyramidal the bond angles would be 107 degrees because of the lone pair repressing the bonding pairs.
Tue Jun 05, 2018 1:00 pm
Forum: Hybridization
Topic: Energy levels
Replies: 6
Views: 425

### Re: Energy levels

Every example that I have done both with my TA and in book the answer has just been sp, sp^3, etc. So I am assuming that is sufficient for the answer.
Wed May 30, 2018 11:30 am
Forum: Determining Molecular Shape (VSEPR)
Topic: lone pairs
Replies: 5
Views: 373

### Re: lone pairs

The reason the molecule is bent is because the repulsion between the two bonding pairs is less than it would be between either bonding pair and the lone pair. This causes the molecule to no longer be linear and take on the bent shape.
Wed May 30, 2018 11:24 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond angles and lone pairs
Replies: 4
Views: 383

### Re: Bond angles and lone pairs

Lone pairs repel the bonding angles because the repulsion strength between a lone pair and a bonding pair is greater than two bonding pairs. Therefore with the addition of more lone pairs forces the bonding electrons closer together.
Wed May 30, 2018 11:19 am
Forum: Determining Molecular Shape (VSEPR)
Topic: General Molecular Shape
Replies: 3
Views: 193

### Re: General Molecular Shape

The best thing you can do is start familiarizing yourself with the general formula and associating each individual formula with its name. For example, AX4E is a seesaw shape, therefore every molecule with 4 bonding pairs and one lone pair on a central atom will have a seesaw shape.
Mon May 21, 2018 10:51 am
Forum: Bond Lengths & Energies
Topic: Pentane vs. 2-dimethylpropane
Replies: 3
Views: 1484

### Re: Pentane vs. 2-dimethylpropane

Pentane is ultimately able to have more van der waal interactions due to its rod shape creating a stronger "bond" between the two molecules so it takes more heat to break them apart.
Mon May 21, 2018 10:48 am
Forum: Bond Lengths & Energies
Topic: Bond strength of molecules [ENDORSED]
Replies: 1
Views: 1961

### Re: Bond strength of molecules[ENDORSED]

If the molecule has resonance structures then the molecule with a greater number of double bonds will have shorter bond lengths. This is because with resonance structures the real bond length is a hybrid of both the single and double bonds (or any other combination), so structures with more double b...
Mon May 21, 2018 10:43 am
Forum: Bond Lengths & Energies
Topic: Van der Waals [ENDORSED]
Replies: 4
Views: 364

### Re: Van der Waals[ENDORSED]

Van der Waals is an interaction because it is just the partial separation of charge. On its own it is very weak, but with a lot of individual interactions between molecules it can be very strong which is why it is sometimes confused for a bond.
Wed May 16, 2018 7:58 pm
Forum: Lewis Structures
Topic: Ionic Lewis Structures
Replies: 2
Views: 243

### Re: Ionic Lewis Structures

In a similar situation, if we look at K^+ and P^3- you would draw Phosphorus in brackets with a full octet and the negative 3 charge in the upper right. However differing from the Na+ Cl- example, there needs to be three K+'s surrounding the P because the phosphorus atom has gained 3 electrons inste...
Wed May 16, 2018 5:50 pm
Forum: Bond Lengths & Energies
Topic: Bond Strength In Same Group
Replies: 6
Views: 1219

### Re: Bond Strength In Same Group

Bond strength is also directly related to atom size. Larger atoms have a larger distance so a longer bond length, and because longer bonds are are weaker, large atoms form weaker bonds. So you can compare bond strength in a group because as you go down a group atom size increases. Therefore CCl4 wou...
Wed May 16, 2018 5:35 pm
Forum: Octet Exceptions
Replies: 6
Views: 506

This means that one electron is not part of a lone pair making the atom unstable. The instability makes the radical so harmful.
Mon May 07, 2018 7:56 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuration for ions
Replies: 2
Views: 304

### Re: Electron Configuration for ions

Therefore the electron configuration for Fe in its ground state would be [Ar] 3d^6 4s^2 and then you remove the two valence electrons from the d orbital to make Fe^2+ which would be [Ar] 3d^5 4s^1 because it is isoelectronic with Chromium.
Mon May 07, 2018 7:44 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Anion electron configuration
Replies: 2
Views: 259

### Re: Anion electron configuration

In addition, cations and anions are most likely not going to lose or gain electrons to a point past the nearest noble gas due to the instability.
Mon May 07, 2018 4:26 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: electron configuration of chromium? [ENDORSED]
Replies: 3
Views: 318

### Re: electron configuration of chromium?[ENDORSED]

Copper also acts similarly to Chromium because it is in the ninth position in the d-block. Therefore instead of its electron's configuration being [Ar] 3d^9 4s^2 it would actually be [Ar] 3d^10 4s^1 because it is more stable.
Tue May 01, 2018 3:57 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: How detailed should the configurations be?
Replies: 3
Views: 223

### Re: How detailed should the configurations be?

The only time where it might be better to write out more of the electron configuration is when it is a noble gas itself or a cation or anion that end up having the same configuration as a noble gas such as O^-2.
Tue May 01, 2018 3:54 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuration of Ag
Replies: 3
Views: 736

### Re: Electron Configuration of Ag

Silver is just like Copper (which we went over in class) because it's in the same group as Silver. Its electron configuration is [Ar] 3d^10 4s^1 rather than [Ar] 3d^9 4s^2 because having a full d orbital is much more stable.
Tue May 01, 2018 3:46 pm
Forum: Quantum Numbers and The H-Atom
Topic: 2.29
Replies: 9
Views: 679

### Re: 2.29

The question for c also does not specify the l value. Therefore we can't assume that it is only the p orbital. This is why both the s and p orbital's electrons should be counted for this question.
Wed Apr 25, 2018 8:32 pm
Forum: Photoelectric Effect
Topic: What is work function? [ENDORSED]
Replies: 15
Views: 3506

### Re: What is work function?[ENDORSED]

In order to find the work function or the threshold energy, you either have to set it equal to the energy per photon if given the lowest frequency or subtract the Ek of the electron from the energy per photon. Often it asks for the threshold energy to be in kJ/mol, however, so then you would have to...
Wed Apr 25, 2018 8:25 pm
Forum: DeBroglie Equation
Topic: When to use DeBroglie or Ek equation
Replies: 7
Views: 458

### Re: When to use DeBroglie or Ek equation

For example, light doesn't have any mass that is why we are unable to use DeBroglie's equation to find E.
Wed Apr 25, 2018 8:23 pm
Forum: DeBroglie Equation
Topic: Module Question [ENDORSED]
Replies: 3
Views: 332

### Re: Module Question[ENDORSED]

This is called destructive interference. In a way the peak of one wave and the trough of one another cancel each other out. However the don't cancel each other out unless their amplitude or the height of the peak/trough are equal and the waves line up perfectly. Otherwise only partial parts of one p...
Wed Apr 25, 2018 8:19 pm
Forum: DeBroglie Equation
Topic: Ek= 0 [ENDORSED]
Replies: 3
Views: 299

### Re: Ek= 0[ENDORSED]

Also if the question gave the minimum energy of the photon required to emit an electron, we would then assume that Ek is equal to zero.
Mon Apr 16, 2018 5:49 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: n energy levels
Replies: 1
Views: 71

### n energy levels

Does the H-atom have a finite number of energy levels. I know that we only specified 1-4 in lecture but n=5 was also mentioned. Is there a way to know how many there are?
Mon Apr 16, 2018 4:57 pm
Forum: Einstein Equation
Topic: einstein equation and other equations [ENDORSED]
Replies: 3
Views: 212

### Re: einstein equation and other equations[ENDORSED]

For example in lecture today, we were asked to calculate the frequency of light emitted by a hydrogen atom as an electron moves to a different quantum level. Without Einstein's equation we wouldn't be able to connect the energy of a photon to calculate the frequency.
Mon Apr 16, 2018 4:51 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Rydberg Constant
Replies: 2
Views: 132

### Re: Rydberg Constant

The equation En= -hR/n^2 is used to calculate the empirical formula for only the H-atom. This is because as a neutral atom it only has one electron. Therefore on the nucleus affects the electron rather than other electrons influencing it too because electrons repel each other. This is why this equat...
Mon Apr 16, 2018 12:00 am
Forum: Properties of Light
Topic: wave length
Replies: 5
Views: 245

### Re: wave length

Amplitude is also related to the electrical field. Therefore as the extent of the change in the electrical field decreases the amplitude decreases.
Sun Apr 15, 2018 11:58 pm
Forum: Properties of Light
Topic: Calculating wavelength [ENDORSED]
Replies: 4
Views: 1041

### Re: Calculating wavelength[ENDORSED]

You would use the equation c=wavelength x frequency. Therefore you would divide the speed of light or c by the given frequency to find wavelength.
Sun Apr 15, 2018 11:56 pm
Forum: Photoelectric Effect
Topic: E(photon)>or=E(energy remove e-) [ENDORSED]
Replies: 2
Views: 164

### Re: E(photon)>or=E(energy remove e-)[ENDORSED]

Basically this means that if the energy to remove the electron is greater than the initial energy harnessed in the photons then electron cannot be emitted.
Sat Apr 07, 2018 12:14 am
Forum: Empirical & Molecular Formulas
Topic: Determining Molecular Formula Based on Name of Molecule [ENDORSED]
Replies: 5
Views: 300

### Re: Determining Molecular Formula Based on Name of Molecule[ENDORSED]

How many of these charges will we have to memorize? Are all the lower numbered elements fair game?
Sat Apr 07, 2018 12:11 am
Forum: Empirical & Molecular Formulas
Topic: Empirical formula [ENDORSED]
Replies: 3
Views: 203

### Re: Empirical formula[ENDORSED]

I agree. I also just use educated guesses. Once you find what number works best, you will remember it for next time so it just becomes second nature.
Fri Apr 06, 2018 11:59 am
Forum: Empirical & Molecular Formulas
Topic: Homework Question
Replies: 4
Views: 373

### Re: Homework Question

I believe that you have to multiply by 3 because it is not close enough to 3. I am pretty sure it has to be greater than 75 to round up.

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