CHEMISTRY COMMUNITY

nicolesalcedo

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.

nicolesalcedo

The VSEPR formula really helps with determining the shape and bond angles!

nicolesalcedo

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.

nicolesalcedo

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.

nicolesalcedo

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...

nicolesalcedo

*texting a chemistry major*

"Hey you wanna go to the movies rn?"

"Sure, when?"

"Rn"

"What do you mean by Radon?"

"..."

nicolesalcedo

To expand, the elements under Flourine in group 17 are all exceptions to the octet rule.

nicolesalcedo

When comparing electronegativity between elements, you can assume that the element that has more valence electrons or a fuller outer shell is more electronegative.

nicolesalcedo

Yes, exactly :)

nicolesalcedo

Anions are opposite from anions; polarizability increases as ions get larger and less electronegative.

nicolesalcedo

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.

nicolesalcedo

Generally, larger molecules are more polarizable than smaller molecules.

nicolesalcedo

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...

nicolesalcedo

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...

nicolesalcedo

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...

nicolesalcedo

How do you determine the number of unpaired electrons if you are given the electron configuration of an element?

nicolesalcedo

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

nicolesalcedo

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?

nicolesalcedo

And just to confirm, those two electrons need to have opposite spins, otherwise they cannot be together?

nicolesalcedo

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?

nicolesalcedo

sorry, correction: the wave model is on wavelength and frequency* (not amplitude)

nicolesalcedo

Yes, exactly :)

nicolesalcedo

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...

nicolesalcedo

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.

nicolesalcedo

Mainly, I think the main topics would be find the molarity, find the concentration of ions, molecules, etc.

nicolesalcedo

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

nicolesalcedo

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?

nicolesalcedo

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...

nicolesalcedo

In practice problem E25, it asks about the number of formula units in 0.750 mol KNO3. What are formula units?

nicolesalcedo

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.

CHEMISTRY COMMUNITY

Search found 30 matches

Re: Post All Chemistry Jokes Here

Re: Bond angles

Re: regions of e- density

Re: Bond Angles

Re: Lone Pairs

Re: Post All Chemistry Jokes Here

Re: Group 17

Re: Calculating electronegativity

Re: Polarizability

Re: Polarizability

Re: Polarizability

Re: Polarizability

Re: Identifying elements in Lewis structures [ENDORSED]

Re: Name to Bond [ENDORSED]

Re: Which atom to have the charge in lewis structures

Unpaired Electrons from Electron Configurations [ENDORSED]

Re: Isoelectric Atomic Radii

Re: Electrons in an Orbital [ENDORSED]

Re: Electrons in an Orbital [ENDORSED]

Electrons in an Orbital [ENDORSED]

Re: Wave vs. Particle

Re: Wave vs. Particle

Re: Wave vs. Particle

Re: Wave vs. Particle

Re: STEPS to figuring out solutions/ molarity quesitons

Re: Value of Speed of Life [ENDORSED]

Re: Formula Units

Re: Formula Units

Formula Units

Re: Length Units