CHEMISTRY COMMUNITY

Alexandra Wade 1L

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.

Alexandra Wade 1L

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.

Alexandra Wade 1L

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.

Alexandra Wade 1L

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.

Alexandra Wade 1L

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.

Alexandra Wade 1L

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.

Alexandra Wade 1L

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.

Alexandra Wade 1L

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.

Alexandra Wade 1L

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...

Alexandra Wade 1L

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.

Alexandra Wade 1L

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...

Alexandra Wade 1L

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...

Alexandra Wade 1L

This means that one electron is not part of a lone pair making the atom unstable. The instability makes the radical so harmful.

Alexandra Wade 1L

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.

Alexandra Wade 1L

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.

Alexandra Wade 1L

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.

Alexandra Wade 1L

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.

Alexandra Wade 1L

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.

Alexandra Wade 1L

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.

Alexandra Wade 1L

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...

Alexandra Wade 1L

For example, light doesn't have any mass that is why we are unable to use DeBroglie's equation to find E.

Alexandra Wade 1L

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...

Alexandra Wade 1L

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.

Alexandra Wade 1L

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?

Alexandra Wade 1L

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.

Alexandra Wade 1L

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...

Alexandra Wade 1L

Amplitude is also related to the electrical field. Therefore as the extent of the change in the electrical field decreases the amplitude decreases.

Alexandra Wade 1L

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.

Alexandra Wade 1L

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.

Alexandra Wade 1L

How many of these charges will we have to memorize? Are all the lower numbered elements fair game?

Alexandra Wade 1L

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.

Alexandra Wade 1L

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.

CHEMISTRY COMMUNITY

Search found 32 matches

Re: HW 4.19

Re: VSEPR

Re: Trigonal Planar vs Trigonal Pyramidal

Re: Energy levels

Re: lone pairs

Re: Bond angles and lone pairs

Re: General Molecular Shape

Re: Pentane vs. 2-dimethylpropane

Re: Bond strength of molecules [ENDORSED]

Re: Van der Waals [ENDORSED]

Re: Ionic Lewis Structures

Re: Bond Strength In Same Group

Re: Radicals [ENDORSED]

Re: Electron Configuration for ions

Re: Anion electron configuration

Re: electron configuration of chromium? [ENDORSED]

Re: How detailed should the configurations be?

Re: Electron Configuration of Ag

Re: 2.29

Re: What is work function? [ENDORSED]

Re: When to use DeBroglie or Ek equation

Re: Module Question [ENDORSED]

Re: Ek= 0 [ENDORSED]

n energy levels

Re: einstein equation and other equations [ENDORSED]

Re: Rydberg Constant

Re: wave length

Re: Calculating wavelength [ENDORSED]

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

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

Re: Empirical formula [ENDORSED]

Re: Homework Question