CHEMISTRY COMMUNITY

Marty Hockey

For number 20 how do we know whether the expected geometry of the compound is square planar or tetrahedral?

Marty Hockey

Can anyone explain why in 9c.5, b) is monodentate or bidentate but in d) it is only bidentate? Both have double bonded oxygens so I don't understand why d) would not also be either monodentate or bidentate.

Marty Hockey

I was absent from lecture the day before thanksgiving and was hoping someone could tell me which topics were covered in that lecture. Thank you

Marty Hockey

The only information we will have on the final will be the same equation sheet we have had for the previous exams, and there is no ligand naming sheet on it so it is extremely unlikely one would be provided.

Marty Hockey

You use bis, tris, etc. when there is a greek prefix already in the name such as the di in ethylenediamine which is one of the examples we could see on the final.

Marty Hockey

For naming compounds, how am I supposed to know which roman numeral to use for the metal atom/ion?

Marty Hockey

I would start out drawing the Lewis structure because that will determine whether or not a molecule is polar and capable of a hydrogen bond. If you draw it out and it is not symmetrical you know it is polar, and if it has an OH, NH, or HF bond than you know it is capable of a hydrogen bond. If anyon...

Marty Hockey

It is asking what kind of interactions these molecules could potentially have. NH2OH, for example, can have hydrogen bonds, dipole-dipole interactions, and London forces because it has an OH bond and is polar. CBr4 can only have London forces because it is nonpolar, and SO2 can have London and dipol...

Marty Hockey

Yes, for example, SO2 is angular with one lone pair so its angles are slightly less than 120 degrees.

Marty Hockey

You can determine whether or not a molecule is capable of hydrogen bonds based on if it has an OH, HF, or NF bond or not as is the case for 3f1a, it is London forces for b) because it is nonpolar so it can't be a dipole, and it can have a dipole-dipole moment for d) because it is polar. Hope this he...

Marty Hockey

Less than 120 degrees if the molecule has one lone pair, and less than 109.5 degrees it the molecule has two lone pairs.

Marty Hockey

For Test 2 are we being tested on all different parts of 3F, of only 3.4 and 3.5?

Marty Hockey

Dr. Lavelle mentioned in the lecture that the shape and conformation of molecules often determine its biological activity, but I'm confused as to in what way does it determine biological activity?

Marty Hockey

Can anyone reply with the subjects that are being covered on test 2? I'm confused about whether it is cumulative and if not, what specific topics it is covering.

Marty Hockey

Often times you can determine if the molecule is polar or non-polar by examining the symmetry of the molecule to see if they cancel out. If it is not apparent that they cancel out through symmetry calculations should ensue.

Marty Hockey

Repulsion is stronger when electrons are closer and weaker when they are further apart.

Marty Hockey

Electronegativity for a molecule is determined by the difference between the electronegativity of the different atoms. For example, H has an electronegativity of 2.1 and F has an electronegativity of 4.0, so 4.0 - 2.1 = 1.9. HF, therefore, has an electronegativity of 1.9.

Marty Hockey

Does anyone have any recommendations/tips on the best ways to memorize all of the different shapes and angles we need to know for molecular shape?

Marty Hockey

You should know the various trends and understand the exceptions (the column of oxygen) but you do not need to know the electronegativity values of each element.

Marty Hockey

Sorry I should have clarified, this is for an electron not light.

Marty Hockey

Hello, can anyone tell me the steps to go from a given wavelength and work function to frequency?

Marty Hockey

In what situations are atoms allowed to have more than 8 electrons? For example, there have been problems in which an element has four shared bonds and an additional lone pair.

Marty Hockey

Anytime a problem gives you any of the following: frequency, wavelength, energy, mass, frequency, or the velocity of light and asks you to find a different term in the aforementioned list is when you would use the equation.

Marty Hockey

The unit is in meters but is often extremely small so it is expressed in nanometers. For example, you would be given a wavelength of 1.5 x 10^-9 meters which could otherwise be written as 1.5 nm.

Marty Hockey

The larger the radius of the element, the larger the polarizing power. So K would have higher polarizing power than Na, and then Na would have higher polarizing power than Li. The trend for the atomic radius is increasing as you go down a period and decreasing as you go across a row.

Marty Hockey

Terelium and polonium have higher first ionization energies than the elements next to them in group 15, but oxygen, sulfur, and selenium all have lower ionization energies than the elements to their left in group 15. This is because group 16 is the first time that there is a paired electron in the p...

Marty Hockey

When I am drawing Lewis structures such as NO3^-1, am I allowed to have a bar line that signals two electrons on the oxygen instead of two dots, or does it always have to be the two dots? It's faster and less tedious.

Marty Hockey

The formal charge of an atom indicates gain or loss of electrons while forming a covalent bond. To determine formal charge, count the number of shared electrons (s), count each number of lone pair electron (L) and then follow the formula: FC (formal charge) = V (valence electrons) - (L + s/2)

Marty Hockey

Essentially all you need to do is follow the electron configuration to the according element. So |Ar|3d7 would take you to the row following Argon (the 4th row) and since it is only 3d7 you just need to count 7 elements from the furthest d point which would be from Scandium to Cobalt, leaving you wi...

Marty Hockey

Bi +3: The previous noble gas for Bi is Xenon so it starts out with |Xe| and then because it is in the 6th row we have to factor in the 4f column so the next sequence is |Xe|4f^14, following that we factor in the next d row as we normally would so |Xe|4f145d10, and then we add in the 6s as that is t...

Marty Hockey

The units are kj/m or kilojoules per mole, or electron volts

Marty Hockey

When filling the spins of electrons in a problem, for example filling the p shell, does it matter which spaces have arrows first? I know that you have to fill the 3 spaces before being allowed to add a second arrow, but does it matter which space you would put the 4th arrow in?

Marty Hockey

When filling the spins of electrons in a problem, for example filling the p shell, does it matter which spaces have arrows first? I know that you have to fill the 3 spaces before being allowed to add a second arrow, but does it matter which space you would put the 4th arrow in?

Marty Hockey

I understand that if there were more than one electron in an orbital they would need to be in separate orbitals, but is the determination of which orbital the electron falls into arbitrary? As in could the first electron fill 2pz, the second 2px, or really any order as long as they're in different o...

Marty Hockey

What is the purpose of writing the electron structure of carbon as 1s^2 2s^2 2px^1 2py^1 as opposed to 1s^2 2s^2 2p^2?

Marty Hockey

Does anyone know if we are supposed to have knowledge of how a lot of the equations we use (De Broglie, Rydberg, etc.) were derived?

Marty Hockey

I understand that if 2 electrons are paired they have opposite spin, and if they're parallel they have the same spin, but what makes the electrons paired or parallel?

Marty Hockey

I believe the group comes from an electron making a transition between two energy levels in an atom.

Marty Hockey

When using the DeBroglie equation, do the units for mass have to be in grams, and does the velocity have to be in meters per second?

Marty Hockey

What is the equation used to determine the wavelength of gamma rays? Used for problem 1B.5

Marty Hockey

The reason the answer is C is that to cause a change in the electrical field you need a sufficient amount of energy to cause this change. When you decrease the frequency you are decreasing the energy and thus making it more difficult to cause change so there is either less change or no change at all...

Marty Hockey

What I've found helpful so far has been writing down or taking note of any questions I have as I'm going through problems. Anytime I have a hiccup or even slight confusion whether it be in lecture or homework, I try to make a note of it so that I can ask for clarification later on down the line. Thi...

Marty Hockey

Hello just wondering what day of the week are we supposed to have had 5 posts written on chemistry community? Additionally, are we shifting to turning in homework during discussion or are we going to continue turning them in after lecture on Friday? Thanks.

Marty Hockey

Incident light can be reflected, absorbed, or transmitted through a sample. The way the incident light changes during an interaction with a sample is characteristic of the substance and can be measured by a spectrometer.

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Before the 1960s, the standard of measurement for a mole was based on Oxygen. Developments in mass spectrometry allowed scientists to find the number of atoms in 12 grams of carbon. In 2018 at a science conference in France they decided that one mole of a substance would be redefined as "6.022 ...

Marty Hockey

K = C + 273.15

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Molar mass is the mass of one mole of an element while atomic mass is the mass of an atom at rest. However, the mass number on the periodic table is both the atomic weight and molar mass for elements (the molar mass and atomic weight of carbon is 12.011g/mol).

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