CHEMISTRY COMMUNITY

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VSEPR gives us three-dimensional geometry. This is important because it helps us know whether a molecule is polar or nonpolar

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Because of the overlap, sigma bonds are stronger. They are also more flexible, where pi bonds are more rigid.

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T-shape has two lone pairs and 3 bonded pairs; the geometry is trigonal bipyramidal

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Cis molecules are polar because the molecules are arranged in a way where the geometry does not cancel out. Trans molecules are nonpolar

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This is a cumulative final, so it includes everything from the beginning of the Quarter, including fundamentals

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Because SiF4 is nonpolar, it has lower intermolecular forces than Si2F2 which is polar.

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Yes, there are still lone pairs even if you can't see them. That is the organic chemistry short hand.

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No, that part is not needed.

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All different parts

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I'm kind of confused on the difference between axial and equatorial and what we need to know about them. Thank you!

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Initially, you should have a pretty good idea as to whether or not a molecule is polar based on electronegativity differences, however polar bonds can be canceled out by geometry. To be sure, I always draw the lewis structure because it helps me, but if you are confident without drawing it than that...

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Because there aren't many things you can calculate in this section, I'm fairly confident that the questions will be mainly conceptual. That being said, the tests are usually easier than the midterms, but I don't think it will be easier or as easy as test one. My advice is to just study your notes an...

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The notation would be AX3 because there are three atoms attached to Nitrogen in the Lewis structure. The amount of bonds does not really matter, but the amount of atoms surrounding the central atom is relevant. The geometry is trigonal planar.

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AsF3 is not polar because even though there are dipole moments, the geometry cancels out. Polar molecules have higher boiling points than nonpolar molecules.

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Approach this molecule as if there are two separate molecules. One of the Carbons is attached to another Carbon along with two Hydrogens. This makes that part of the molecule trigonal planar with a bond angle of 120 degrees. The bond angle between the two carbons is 180 degrees.

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A coordinate covalent bond is a bond formed between a Lewis Acid and a Lewis Base. A lewis acid (usually elements like Boron and Aluminum whose full shell consists of 6 not 8 electrons) accepts electrons from a lewis base. The base donates two electrons opposed to just one to form a bond. By doing s...

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Yes. When you have a Lewis acid and a Lewis Base you form a molecule comprised of at least one coordinate covalent compound.

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They are the same thing. The first equation you listed is just a simplified version of the second equation; it is useful because you can just plug in your values and get your answer essentially in one step. Professor Lavelle said he doesn't really like the equation though because he feels as though ...

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Only some compounds have Lewis Acids and Bases. Usually elements like Boron, Aluminum etc. are lewis acids because they don't follow the octet rule and only have 6 electrons in total (opposed to 8). When this happens, another element will donate two of their electrons to the bond instead of just one...

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There is only one exception and that is when there is resonance. In resonance structures, though it appears as though some of the bonds are double bonds and some are single bonds, in reality, the bond lengths are all the same length and have the same strength-- the length is the average of the lengt...

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When I do Lewis structures, what works for me is not looking at what each atom is contributing, but rather looking at the total amount of valence electrons as a whole. Yes, you are right in thinking that Oxygen usually has two bonds and that results in the oxygen having a formal charge of 0. However...

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There is, but it depends if you are analyzing the anion or the cation. When analyzing the cation, smaller atomic radius + higher charged cations have a higher polarizing power. This is because they have a stronger pull on the electrons of the anion they are bonding with. When looking at the anion, l...

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If a structure has resonance, you should probably draw it because the actual representation of the molecule is the average of all lewis structures. Thus, it is not correct to include only one form of the Lewis structure because it is not a completely accurate representation of the molecule. Though t...

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The exceptions to electron configurations are Chromium and Copper. Basically, in these two elements, you do not fill up the 4s shell first. Instead, you put one electron into the 4s shell and then move on to the 3d shell. So Cr's electron configuration is [Ar] 3d5 4s1 and Cu is [Ar] 3d10 4s1. The wa...

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Exceptions to the octet include: H, He, Li, Be, B, and anything after the first two rows of the periodic table. The octet rule does not really apply to the majority of the periodic table. Because Br is after the second row of the periodic table, it usually has more than 8 electrons when it is the ce...

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When I was trying to write the electron configuration for Bi^3+ I did not know why the answer key included 14f in this configuration. How would I find out what the correct configuration is for Bi^3+?

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Lowest Ionization energy means that the atomic radius is larger, thus it is easier to pull the electrons away from the nucleus. For this reason, they are better at bonding with other atoms.

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In molecules like that, the Carbon is almost always going to be the central atom due to how many bonds it can hold (this is also what organic chemistry mainly focuses on-- Carbon molecules). Carbon Molecules can have 4 bonds as it has 4 valence electrons. Oxygen has 6 valence electrons and only need...

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Basically, Lewis structures are an oversimplification of what the molecule actually looks like. There can be multiple ways to draw the same structure (doesn't just have to be three ways, but can be 2+) because the molecule is constantly switching which bonds are double and single. This also explains...

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Double bonds are stronger and shorter because they share more electrons than single bonds, thus there is a stronger pull between the two atoms that are bonded. A good way to think about this is holding on to a ball with one hand vs with two hands. If you are only holding onto the ball with one hand,...

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Combustion always results in CO2 and H2O.

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Balance what there is less of first. Also, keeping continuous track of what each side has and being organized helps a lot.

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Accuracy is how close you are to the actual desired amount. Precision describes more the consistency of your work ethic. You can be precise but still not be accurate as a result of malfunctioning lab equipment.

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Nodal planes are where the probability of finding an electron is 0. You find these areas by using Schrödinger's equation.

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The only reason why these configurations do not follow the original rules is that if they did, the energy would not be distributed symmetrically. The d subshell has 5 orbitals that hold 2 electrons each. It helps to think about it visually. Draw out the 5 orbitals for the d shell and fill it in and ...

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Constructive is when the peaks of two of the waves do not clash, combine, and then result in a larger wavelength. Destructive is when the peaks of two wavelengths do not line up, combine, and result in a smaller wavelength. If the trophs are the same size, they will cancel out completely. I recommen...

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I was looking over modules and reached the last one. Will he post more modules or is that it?

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Why is the quantity of the mole based on a Carbon atom instead of elements like Oxygen or Nitrogen?

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Hi! Does anyone know if and when we will get our first test back? Also, someone told me that he will not put in those grades until the very end of the Quarter. Is that true?

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In the ultraviolet spectrum of atomic hydrogen, a line is observed at 102.6 nm. Determine the values of n for the initial and final energy levels of the electron during the emission of energy that leads to this spectral line.
Is it possible for me to solve this without using the Rydberg equation?

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Just remember that something becomes- ide when it is gaining or losing electrons (when it's an ion).

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Something that really helps is staying organized. When I balance my equations, I list every atom that the equation has and how many of each atom there is. For example, if the equation you have to balance is N2 + O2 yields NO I will write down N and O in a vertical line. I will then put the number 2 ...

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You can do whatever is relevant to the class. Because we have a test on Tuesday over general chem, we can still submit homework in the fundamentals section.

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You have to think of each of these terms as a unit. Even though molecules have more atoms, they are still joined, thus they are one unit. The same thing applies to formula units. This is why Avogadro's number applies to all of it. An easy way to think of Avogadro's number is the same way to think ab...

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The Question is: a 1.50-gram sample of metallic tin was placed in a 26.45 g crucible and heated until all the tin had reacted with the oxygen in the air to form an oxide. The product weighs 1.9g. a) What is the empirical formula of the oxide? b) Write the name of the oxide. ---- I don't really know ...

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