CHEMISTRY COMMUNITY

serenabirkhoff_1K

Light hits a sodium metal surface and the velocity of the ejected electron is 6.61 x 105 m.s-1. The work function for sodium is 150.6 kJ.mol-1. Given this info the part b asks How much energy is required to remove an electron from one sodium atom? If it helps the previous question asked What is the ...

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Ok so for lone pairs, do we just look at the regions of electron density and determine they hybridization for just that atom? For example, if I was given a N with 3 regions of electron density (one region being composed of a lone pair), would I write N= 2sp 2 ? Yes, to find the hybridization just c...

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Camille 4I wrote:What makes for a higher boiling point, ion-dipole interactions or hydrogen bonding?

Ion-dipole interactions are the strongest intermolecular force and therefore stronger than hydrogen bonding and therefore ion-dipole interactions have a higher boiling point.

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Sigma bonds are stronger and this makes sense because if the molecule rotates pi bonds will be broken.

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In addition to the problem above when the molecule is an oxoacid when drawing the lewis structure the hydrogen will be attached to the oxygen, even when the oxygen is not the central atom.

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AnnikaMittelhauser4E wrote:I think you might be misreading the answers. Aqua always refers to water, which can be written as either H2O or OH2 (which I think you're mistaking for OH-). The textbook writes water as OH2 to emphasize the oxygen is doing the bonding I believe.

Thank you this makes a lot more sense now!!

serenabirkhoff_1K

For number 4 how does the hybridization become sp2 if there are 4 p electrons and 2 s electrons? If you draw the lewis structures you will see there are 3 regions of electron density around S, one lone pair and 2 bonds with 0. (remember a double bond still counts as one region of electron density)....

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When given the name and expected to write the formula for coordination compounds how do you know when given aqua to use H2O or OH-
For Example in 9c.3 part 3 has aqua and in the answer it says to use H2O but in part d aqua is in the name but they use OH- when writing the formula.

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You would do well to memorize the table. If you forget you can try drawing the Lewis structure to figure it out, but this is difficult for more complicated ligands https://lavelle.chem.ucla.edu/wp-content/supporting-files/Chem14A/NamingCoordinationCompounds.pdf is this the table you are referring t...

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It is cumulative and I would make sure to know everything on each of the outlines as well as be able to do the problems on them. All the outline and the problems are on his website.

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If we use the roman numeral for positive cations what do we use if the transition metal has a negative anion charge? will this happen?

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For part b i meant to put that it is BH3 so that would change the reasoning would it still be the case with this?

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When doing a hybridization problem like 2F5 part b (it says to identify the hybrid orbital for BrF3) is it possible for the lewis structure to not satisfy the octet rule? and to solve this problem do you just count the numbers of electron density?

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Thank you so much. I was a bit confused on the difference, but this helped a lot.

serenabirkhoff_1K

I think that we will be given the same information on the final as the tests and midterms. For learning how to name the coordination compounds, Dr. Lavelle posted a sheet for this on his page, which I think we must memorize/learn for the final. Here is the sheet. https://lavelle.chem.ucla.edu/wp-con...

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In addition to the link given above with the pdf of how to name compounds and what names we should know shared by Dr. Lavelle, I would also suggest doing the practice problems on outline 5 to understand better what compounds we will be expected to name and also have practice naming them, and then ho...

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Additionally, there is a table on page 113 in the textbook that helped me a lot with understanding polar and nonpolar. It also helped visualize polar and nonpolar with the shape of the molecule and VSEPR formula, withe examples. The figure is 2E.7 on page 113.

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Bent and angular are interchangeable terms for the same type of shape. Both work when naming AX2E and AX2E2 molecules. Additionally, AX2E and AX2E2 are both bent/angular shape but have different angles depending on how many electron pairs they have. AX2E has one electron pair and the bond angles are...

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For week 9 I am assuming we still have to do 5 problems. When do we turn in our homework if we do not have section? Do we just turn it in to our TA during lecture or the following week do we turn in week 9 and 10.

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For next week (week 9) I think we can do outline 5 and the start of outline 6.

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We are definitely supposed to memorize all the shapes we learned in class. As well as what we learned after like bond angles and how they can change based on lone pairs.

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I would just worry about what we learned for right now, but he said he will be going over more in Fridays lecture so he might go over those then, and then they will probably be on the test.

serenabirkhoff_1K

I am not sure exactly what you mean, but when drawing the lewis structure you have to arrange the atoms equally distant from the central atom and then once you do this you can determine the name of the shape based on the arrangement of the atoms. For example, the a linear or trigonal planar shape ba...

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Yes definitely memorize the names he said when asked questions on this topic we will have to name the shape.

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Thank you! So glad it is only on the topics covered after the midterm.

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I found this definition for a dipole moment and it helped me a lot hope it helps. When atoms in a molecule share electrons unequally, they create what is called a dipole moment. This occurs when one atom is more electronegative than another, resulting in that atom pulling more tightly on the shared ...

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Julieta Serobyan4D wrote:My TA told me it's going to include VSEPR, IMF, polarity and bonding.

Have we covered IMF in class yet? what section in textbook is it?

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What section is intermolecular forces?

serenabirkhoff_1K

Do we need to know formulas for certain chemical compounds like Ammonium? One of the homework problems asked to draw a lewis structure with ammonium and another element but did not give you (NH4+). Will we need to know this for the midterm and if so which others should I memorize? I know he said to ...

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If you have an odd number of electrons like when oxygen makes one bond and then has 5 extra electrons there is one extra electron to create 3 lone pairs of electron so you can create a double bond to have 4 electrons which is an even number for the lone pairs

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for me the easiest way to remember how to calculate formal charge is the formula. At first I was having trouble remembering but once you do enough practice problems with the formula you should remember it.

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For D.19 use the table 2d11 with the given the radii for each element and add the two radii together to get your answer. For example for part A you get from the graph 77pm for C and 58pm for F and then just add them together to get the answer 135pm

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FC = [# of valence electrons on atom] – [(# of lone pair electrons) + (# of shared electrons)/2] Formal charge helps you predict which structure is the lowest energy structure. The closer the formal charges are to 0 on the atoms the lower the energy of the structure. It is important to calculate for...

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Yes the midterm covers all material up to the end of Focus 2D in Outline 3: Chemical Bonds.

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The atom with the lowest ionization energy goes in the middle. Remember that ionization energy increases as you move up and right on the periodic table. Ionization energy is the minimum amount of energy required to remove the most loosely bound electron.

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He said in lecture that we have not learned angles yet and we will learn it later so right now drawing angles is not needed.

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i think you are supposed to do it on the most recent topic but I am sure if you do a few quantum and a few chemical bonding that is okay too.

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To add to this: Electronegativity is how well an atom can attract an electron to itself. This increases as you move right on the periodic table. Electron affinity of an atom or molecule is defined as the amount of energy released or spent when an electron is added to a neutral atom. Electron affinit...

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I don't think there will be any more. I think based on the survey's and how much people liked them he may work on adding more in the future.

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The atomic radius refers to the radius of atoms in ground state (i.e. lowest energy state of an atom, which we can consider electrically neutral). The ionic radius refers to the radius of ions -- atoms with charge -- which are different in size from atoms in neutral state. The ionic radius of an io...

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Someone on another post said this and it helped me hope it does the same! "Atomic spectra are the transitions of electrons between electronic energy levels in isolated atoms. They are affected by interactions of the transitioning electrons with the nuclei spins and with the other electrons in t...

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The 4s orbitals have a lower energy than the 3d, and so the 4s orbitals are filled first. When writing electron configurations the order in the orbitals are filled in increasing order of energy levels so 4s would come before 3d.

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An atom is considered to be a cation when it's lost an electron(s) from its neutral state and is thus positive (a common method used to remember this is that "cats" are paws-itive). On the other hand, if an atom gains an electron(s), it becomes more negative and is considered to be an ani...

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Can someone explain the answer to question 1A.11 I am not sure on the concept here

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This problem has an error in the solution manual.
Here is the link Dr. Lavelle shared
https://lavelle.chem.ucla.edu/wp-conten ... rs_7Ed.pdf

serenabirkhoff_1K

I don't believe that sig figs are too important in this class. My TA told us that sig figs are not too big of a deal, as long as you do not round to whole numbers or to only 1 decimal place when the answer should clearly have 2 or 3 decimal places. As for scientific notation, I believe that it is m...

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a) 3 b) 5 c) 1 d) 7

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The unit of the de Broglie wavelength is meters (m) so when using his formula I think it should be in m but after solving you can convert to nm for the answer if it asks.

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Rich Zodda 4B wrote:What kind of posts count? Like do questions about grading such as this one count?

I think all comments and questions count from what I heard.

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Sanjana Munagala_3k wrote:From what I heard from my TA. It won't really cover fundamentals but will cover the quantum world and chemical bonding!

Hope that helps!

If it covers chemical bonding do you know when we will start learning this since the midterm is coming up?

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Thank you all so much this helped a lot!!

serenabirkhoff_1K

Thank you so much all these responses helped a lot to know the difference in sig figs when using scientific notation like 7.00 x 10^2 versus 7 x 10^2.

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Will we ever have to know the polyatomic ions or always just the simple ones like water and carbon dioxide?

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I always start with what looks most complicated and leave elements that stand alone for last because when adding a coefficient to that element it will not change the amount for others and therefore is easier to change last because then you do not have to go back and add more coefficients to other el...

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How do you convert to angstroms to other units and from other units to angstroms?

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I agree with everything Rebekah said! To add onto it, sig figs are important when calculating your final answer. For example, if you were multiplying two numbers - 2.0 (2 sig figs) and 554.0 (4 sig figs) - your answer would have as many sig figs as the value with the lowest number of sig figs. The ...

serenabirkhoff_1K

I agree with everything Rebekah said! To add onto it, sig figs are important when calculating your final answer. For example, if you were multiplying two numbers - 2.0 (2 sig figs) and 554.0 (4 sig figs) - your answer would have as many sig figs as the value with the lowest number of sig figs. The ...

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I understand it is 5 problems each week but how is it graded? Is it completely by accuracy?

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Each term burning, combustion, oxidation, or metabolism from my understanding are used depending on the molecules that are in that reaction.

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We are required to post 5 comments per week in order to receive full credit correct? How do the TAs check this? Do we show them our comments for the week during discussion?

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305319402 wrote:when would we meet for study groups? also can someone maybe make a groupme for the study group?

I think a group me would be easiest if someone can make one! and we can meet in any of the study rooms around campus I know there are ones you can reserve in the study!

serenabirkhoff_1K

I am interested!! Does anyone know of one already started? If so can I be added? If not we should really start one!

serenabirkhoff_1K

Just like in an math equation what you do to one side you must do to another. The easiest way for me to think about it is if you have a fraction and need to make is a whole number, multiple every coefficient by the denominator of that fraction (including that fraction), in order to get a balanced eq...

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