CHEMISTRY COMMUNITY

Abbey Brandt 1K

The strength of intermolecular forces varies systematically with the type of bond. Like the response above, this is different than looking within the molecules, where bond length is important. Between molecules is when intermolecular forces become a topic of interest. Look at this explanation for fu...

Abbey Brandt 1K

Hi! This isn't a mnemonic (wish I had one), but it is very helpful. There is a lot to remember, so just focus on electronegativity and ionization energy. Those are the big two that affect the rest, so knowing those will give you most of the information you need. Look at this video, too (super helpfu...

Abbey Brandt 1K

I found a post from 2015 that seems to answer your question well: "Hey there! Some molecules can accommodate more than 8 valence electrons because they have expanded valence shells. These molecules are from periods 3 or higher because starting from n=3, atoms have d-orbitals that can accommodat...

Abbey Brandt 1K

Boron has 3 valence electrons, meaning it wants to gain 5 to fill its octet. The issue here is that there are no observed cases in which Boron shares 5 electrons with another atom to achieve the goal of a full octet (Boron can only make 3 covalent bonds and is thus satisfied with a "sextet"...

Abbey Brandt 1K

For a more in-depth analysis of your question, I would take a look at this article: https://brilliant.org/wiki/sigma-and-pi-bonds/ Understanding the difference between sigma and pi bonds is important in understanding the molecular orbital theory, which will in turn help you with structural and orbit...

Abbey Brandt 1K

I have always been confused by this as well. I know that there are often multiple ways to show an atom's structure, and that the best one has a formal charge of 0, but WHY? How do you know how many resonance structures to draw? Any and all insight is welcome.

Abbey Brandt 1K

Hi, To my understanding, Z is not one of the four types of quantum numbers [those are principal quantum number (n), the orbital angular momentum quantum number (l), the magnetic quantum number (ml), and the electron spin quantum number (ms)]. Z, in this context, is involved with the quantum number m...

Abbey Brandt 1K

Hi! Great question. Typically, Dr. Lavelle will specify whether or not he wants the full, Noble Gas, or shorthand notation as an appropriate answer to a test question. To be safe, I would default to the full configuration. But look out for specific language of test questions that will prompt you to ...

Abbey Brandt 1K

The above answer is a great explanation of the listed subject, but I'm not sure it's what you were looking for. I do not believe this was covered explicitly in lecture, but regardless it is an important subject to understand for future chemistry topics. I don’t know if you plan on continuing your ch...

Abbey Brandt 1K

Hi, For the 4s orbital n+ l = 4 + 0 = 4. For the 3d n+l = 3 + 2 = 5. So 4s is lower in energy so fills first.After calcium the 3d orbital falls below the 4s in terms of energy. This means the 4s electrons are lost first in chemical reactions and define the atomic radius of the atom. In summary, repu...

Abbey Brandt 1K

Hi everyone, I am having trouble accessing the guidelines for posting on this site. I see on the course website that we must post clear questions and answers every week, but I blanked on how many we need to post and if extra posts carry over to the following week. For example, if we were required to...

Abbey Brandt 1K

For the above reasons, always remember that actual yields are less than theoretical yields. That is a great rule of thumb if you mix up calculations; the theoretical yield should never be smaller!

Abbey Brandt 1K

The best rule I can give you is to use the least specific number of sig figs used in the question itself. For example, if in the equation there are measurements including the digits 4.98, 5.667, and 0.2, you would use 1 significant figure. Does that help?

Abbey Brandt 1K

Hi all, I agree with above, however, you should be aware of the basic naming rules including prefixes and suffixes. These are very important in your chemistry career, and is this is only a review of high school chemistry topics, don't be surprised if they show up on the test and something isn't prov...

Abbey Brandt 1K

Hi all, I was in this class for a few weeks before it became necessary for me to go home on medical leave. I would recommend knowing the sig fig rules, even though they will not be graded harshly on the test. It is a useful skill moving forward and will definitely be useful in later chemistry and ma...

Abbey Brandt 1K

Hello all, I was in this class for a few weeks before I had to go home on medical leave. This unit is only a review of high school chemistry, so you should be aware of most of the naming rules. As is stated above, the prefixes and suffixes are important to know. If I remember correctly, you don't ne...

Abbey Brandt 1K

For the 4s orbital n+ l = 4 + 0 = 4. For the 3d n+l = 3 + 2 = 5. So 4s is lower in energy so fills first.After calcium the 3d orbital falls below the 4s in terms of energy. This means the 4s electrons are lost first in chemical reactions and define the atomic radius of the atom. In summary, repulsi...

Abbey Brandt 1K

I see that this question was posted a little while ago, but an answer may be helpful to current 14A students. At the first energy level, the only orbital available to electrons is the 1s orbital, but at the second level, as well as a 2s orbital, so this is what the 2 means in the question.

Abbey Brandt 1K

The following is taken from an extremely useful chemistry article that explains how p-block elements differ from the others we learn about. I hope this helps: The difference in inner core of elements greatly influences their physical properties (such as atomic and ionic radii, ionisation enthalpy, e...

Abbey Brandt 1K

Here is a list of all of the most important to know: From left to right across a period of elements, electronegativity increases. If the valence shell of an atom is less than half full, it requires less energy to lose an electron than to gain one. Conversely, if the valence shell is more than half f...

Abbey Brandt 1K

For the 4s orbital n+ l = 4 + 0 = 4. For the 3d n+l = 3 + 2 = 5. So 4s is lower in energy so fills first.After calcium the 3d orbital falls below the 4s in terms of energy. This means the 4s electrons are lost first in chemical reactions and define the atomic radius of the atom. In summary, repulsiv...

Abbey Brandt 1K

As the previous comments clarify, you will not be asked to draw orbitals, but I would be familiar with their general shape, planes, etc. for future chemistry courses (if you plan to stay in this series). It is a cool skill to have and helps make a very foreign, complex more tangible when you can vis...

Abbey Brandt 1K

I am not certain what you are asking, but I will do my best with my interpretation of the question! Valence electrons are the electrons in the outer-most orbital that is not completely filled. The nucleus (center) of the atom contains the protons (positively charged) and the neutrons (no charge). Th...

Abbey Brandt 1K

s, p, d, and f are all included in electron configurations when the element is in a certain position on the periodic table. The sum of the superscripts in an electron configuration is equal to the number of electrons in that atom, which is in turn equal to its atomic number. I would refer you to thi...

Abbey Brandt 1K

He (Helium) has two electrons in its outer level. Look at its placement on the periodic table. Since there is no 1p subshell, 1s is followed immediately by 2s, and so level 1 can only have two VE at the most. H only needs one additional electron to be stable, and can accomplish this through covalent...

Abbey Brandt 1K

Another recommendation I have for you is to get the Student Solutions Manual that Dr. Lavelle wrote with two others. It is very helpful in detailing solutions and, if you're like me, working backwards from an answer when you can't figure out where to start. I hope this helps!

Abbey Brandt 1K

Take a look at some of the highlighted sections on Dr. Lavelle's course website! There are some outlines that very effectively describe the sections covered and what problems correspond to each topic. Even better is the course reader that is not required, but very much helps with this confusion. I h...

Abbey Brandt 1K

For my own sake and that of everyone in this class - what do you find to be the most effective way to take notes in this class? Google Docs, handwritten, custom outline, whatever it may be - share it! Understanding what helps you all succeed will help us all understand more effectively and in turn p...

Abbey Brandt 1K

Dr. Lavelle has posted an outline for Test 2 which includes problems from the sections the test will cover. I would recommend going through those problems and completing all recommended/required readings for the best preparation! Good luck :)

Abbey Brandt 1K

Hi Caitlin! I used to be very confused about significant figures, so I completely understand where you're coming from! The reason the number of significant figures varies so much in the solutions manual is because every problem gives you a different level of specificity to begin with. If the problem...

Abbey Brandt 1K

Hi Alicia, I was told earlier that all we are allowed to use on exams is a simple calculator. I would assume this means no formula sheet, especially for this test where the key concepts in all previous lectures have highlighted important formulas. My strategy, if I were you, would be to memorize the...

Abbey Brandt 1K

Hi all, I am currently registered with the CAE, where I am granted testing accommodations for learning disabilities. I am a little bit unsure, however, of how to approach the short tests that are given during discussion sections. In previous courses, the only tests given were midterms and finals, bu...

Abbey Brandt 1K

To my understanding, modules for this section (Review of Chemical and Physical Principles) should be completed by the end of week 2 (Sunday, October 14). They are completed anonymously, but I believe the instructor has access to a list of who has completed them to assign credit. I may be incorrect, ...

CHEMISTRY COMMUNITY

Search found 33 matches

Re: Intermolecular forces

Re: Mnemonics for the period table trends

Re: Valence Shells

Re: Boron's valence electrons

Re: Significance of Sigma and Pi Bonds

Re: Resonance Structure meaning

Re: Quantum Number Z

Re: Short Hand or Normal Way?

Re: Probability of finding an electron at a certain location

Re: Why is 4s before 3d?

Chemistry Community Posts

Re: Actual Yield vs Theoretical Yield

Re: Rounding

Re: Compound names

Re: Next Week's Test 1

Re: Formula Names

Re: electron config. 3d and 4s

Re: Composition of a bond (Sigma and Pi Bonds)

Re: P-block elements

Re: Trends in the Periodic Table

Re: electron config. 3d and 4s

Re: Sketching orbitals

Re: Valence shell and other electrons

Re: electron configurations

Re: Octet Exceptions

Re: Homework 2B.21

Re: Chapters 1 and 2 logisitcs

Note Taking

Re: Test 2

Re: Rounding Using Significant Figures

Re: Formula Sheet?

Accommodation on Section Tests

Re: Modules?