Search found 36 matches

by Kandyce Lance 2L
Sun Nov 22, 2020 11:37 pm
Forum: Resonance Structures
Topic: Dominant Contribution to Resonance Hybrid
Replies: 3
Views: 18

Re: Dominant Contribution to Resonance Hybrid

Is it possible to have two different resonance structure that are equally "most beneficial"? For example moving the position of a double bond has the same exxfect for each position bc they dont affect formal charge? Just the position of the charges?
by Kandyce Lance 2L
Sun Nov 22, 2020 11:28 pm
Forum: Formal Charge and Oxidation Numbers
Topic: oxidation numbers
Replies: 4
Views: 29

Re: oxidation numbers

Oxidation numbers, also called oxidation states, are the total number of electrons that an atom either gains or loses in order to form a chemical bond with another atom. An oxidation number can be assigned to a given element or compound by following the following rules: - The oxidation number of a ...
by Kandyce Lance 2L
Sun Nov 22, 2020 11:26 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 18
Views: 45

Re: Bond Angles

I have an additional question relating to bond angles, For two molecules with the same shape (like an AX_3 for example), will all the bond angles be the same? Or will they change depending on the individual elements? I understand bond angles with be slightly different with lone pairs vs no lone pai...
by Kandyce Lance 2L
Sun Nov 22, 2020 11:24 pm
Forum: Lewis Structures
Topic: Octet Rule
Replies: 13
Views: 43

Re: Octet Rule

I was having some trouble drawing lewis structures recently because I would often find myself with (usually 2) extra electrons. After I had already filled the outer elements to 8. It was in a recent lecture that Dr. Lavelle put the lone pairs on the elements in the middle and I never thought to do ...
by Kandyce Lance 2L
Sun Nov 22, 2020 11:23 pm
Forum: Lewis Structures
Topic: Octet Rule
Replies: 13
Views: 43

Octet Rule

I was having some trouble drawing lewis structures recently because I would often find myself with (usually 2) extra electrons. After I had already filled the outer elements to 8. It was in a recent lecture that Dr. Lavelle put the lone pairs on the elements in the middle and I never thought to do t...
by Kandyce Lance 2L
Sun Nov 22, 2020 11:17 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 18
Views: 45

Re: Bond Angles

I have an additional question relating to bond angles, For two molecules with the same shape (like an AX_3 for example), will all the bond angles be the same? Or will they change depending on the individual elements? I understand bond angles with be slightly different with lone pairs vs no lone pai...
by Kandyce Lance 2L
Sun Nov 22, 2020 11:16 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 18
Views: 45

Re: Bond Angles

I have an additional question relating to bond angles, For two molecules with the same shape (like an AX_3 for example), will all the bond angles be the same? Or will they change depending on the individual elements?
by Kandyce Lance 2L
Sun Nov 22, 2020 11:14 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 18
Views: 45

Re: Bond Angles

These responses are a bit mixed but I agree, it would be safest to memorize the basic bond angles in the common geometric shapes and planars
by Kandyce Lance 2L
Sun Nov 15, 2020 11:32 pm
Forum: Significant Figures
Topic: All students read this sig fig post [ENDORSED]
Replies: 133
Views: 17404

Re: All students read this sig fig post [ENDORSED]

Jordanmjones13 wrote:Do you know if the problems will specifically tell us how many significant figures to use?



I believe you use the lowest number of sig figs gives from numbers in the question
by Kandyce Lance 2L
Sun Nov 15, 2020 11:19 pm
Forum: Ionic & Covalent Bonds
Topic: Hydrogen Bonding
Replies: 13
Views: 38

Re: Hydrogen Bonding

Since ice is less dense than water, it floats but in alcohol it sinks so is that because alcohol is more dense than ice and also alcohol also takes a very long time to freeze, is this because of the density, or it it caused by hydrogen bonds?
by Kandyce Lance 2L
Tue Nov 10, 2020 6:11 pm
Forum: Ionic & Covalent Bonds
Topic: Lewis Structure
Replies: 3
Views: 27

Re: Lewis Structure

He subtracted 1 electron because the ammonium had a positive charge. This means the ammonium had to lose 1 electron to be positively charged. Thank you! I went back to my notes and I missed where it said -Cation: remove 1e- for each +1 charge -Anion: add 1e- for each -1 charge In case anyone else h...
by Kandyce Lance 2L
Tue Nov 10, 2020 6:08 pm
Forum: Properties of Electrons
Topic: Orbital Energies
Replies: 5
Views: 63

Re: Orbital Energies

My question has more to do with orbitals as a concept, but on a recent lecture Professor Lavelle states that "An orbital is a math function with three quantum numbers: n,l,m" I was a bit confused because I thought orbitals were work functions, not math functions...are they both the same t...
by Kandyce Lance 2L
Tue Nov 10, 2020 5:04 pm
Forum: Ionic & Covalent Bonds
Topic: Lewis Structure
Replies: 3
Views: 27

Lewis Structure

Ammonium, NH₄⁺
N- 5e-
O- 1e- x 4 = 5
then add
5 + 4 = 9
but in this example we ended up with 8e-


In the Ammonium example from lecture why did Dr. Lavelle subtract 1 to get 8e-? I thought we were just adding..
by Kandyce Lance 2L
Tue Nov 10, 2020 4:57 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Ionization Energy
Replies: 2
Views: 9

Re: Ionization Energy

From lecture, Dr. Lavelle used this example to show that removing the 2nd e- will always take more energy Cu(g) --> Cu^+(g) + e-(g) l_1 = 745.1 kJ.mol^-1 Cu^+(g) --> Cu^2+(g) + e-(g) l_2 = 1955 kJ.mol^-1 (almost 3x harder) Where is the formula to find the ionization energy? Or is the ionization for...
by Kandyce Lance 2L
Tue Nov 10, 2020 4:57 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Ionization Energy
Replies: 2
Views: 9

Ionization Energy

From lecture, Dr. Lavelle used this example to show that removing the 2nd e- will always take more energy

Cu(g) --> Cu^+(g) + e-(g) l_1 = 745.1 kJ.mol^-1
Cu^+(g) --> Cu^2+(g) + e-(g) l_2 = 1955 kJ.mol^-1 (almost 3x harder)


Where is the formula to find the ionization energy?
by Kandyce Lance 2L
Sun Nov 08, 2020 6:00 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Why is the 4s state filled before the 3d state?
Replies: 14
Views: 89

Re: Why is the 4s state filled before the 3d state?

SahajDole_1G wrote:The 4s shell has a lower energy level than 3d, which is why the 4s shell fills first



So basically, the takeaway from this question is that it doesn't necessarily matter the number being filled in the shell but the energy level?
by Kandyce Lance 2L
Sun Nov 08, 2020 5:59 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Can you have the same 3 quantem number but not the 4 same quantem numbers
Replies: 12
Views: 57

Re: Can you have the same 3 quantem number but not the 4 same quantem numbers

Yes you can have the same 3 quantum numbers since each orbital can hold two electrons. Thus, two electrons in the same orbital would have the same first three quantum numbers but have a different spin state. This is just a clarifying question, but with the last 2e- on the same orbital, one will spi...
by Kandyce Lance 2L
Sun Nov 08, 2020 5:19 pm
Forum: Properties of Electrons
Topic: Orbital Energies
Replies: 5
Views: 63

Re: Orbital Energies

My question has more to do with orbitals as a concept, but on a recent lecture Professor Lavelle states that "An orbital is a math function with three quantum numbers: n,l,m" I was a bit confused because I thought orbitals were work functions, not math functions...are they both the same th...
by Kandyce Lance 2L
Sun Nov 08, 2020 5:15 pm
Forum: Quantum Numbers and The H-Atom
Topic: Pauli Exclusion Principle
Replies: 6
Views: 19

Re: Pauli Exclusion Principle

Kandyce Lance 2L wrote:Can someone clarify expand on why there can be no more than 2e- per orbital?



Does it have to do with not being able to have the same 4 quantum numbers? or are those two topics unrelated?
by Kandyce Lance 2L
Sun Nov 08, 2020 5:13 pm
Forum: Quantum Numbers and The H-Atom
Topic: Pauli Exclusion Principle
Replies: 6
Views: 19

Pauli Exclusion Principle

Can someone clarify expand on why there can be no more than 2e- per orbital?
by Kandyce Lance 2L
Sun Nov 01, 2020 7:58 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Heisenberg Indeterminacy (Uncertainty) Equation
Replies: 5
Views: 90

Re: Heisenberg Indeterminacy (Uncertainty) Equation

Can someone explain why there's an inverse relationship between the certainty of momentum and position for electrons? Based on these responses i understand that as the uncertainty for position goes up, uncertainty in momentum will go down and vice versa but additionally is there anyway the level of...
by Kandyce Lance 2L
Sun Nov 01, 2020 7:35 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Orbitals and Electrons
Replies: 9
Views: 32

Re: Orbitals and Electrons

I also have a question regarding orbitals. From my notes in a previous lecture i have it written that when n=2, l=1 ml=-1 that the electron is in "a 2px state" and i went back and rewatched that portion of th electure but i dont understand what the "px state" is referring to. Doe...
by Kandyce Lance 2L
Sun Nov 01, 2020 7:24 pm
Forum: Photoelectric Effect
Topic: Sapling hw #12
Replies: 5
Views: 48

Re: Sapling hw #12

I forgot to mention that after i would use E=n^1-n^3 and lambda=h/m*v? This is my process when solving this equations so I'm not sure if my calculations are wrong, or if my general set up is. Any guidance is very much appreciated!
by Kandyce Lance 2L
Sun Nov 01, 2020 7:22 pm
Forum: Photoelectric Effect
Topic: Sapling hw #12
Replies: 5
Views: 48

Sapling hw #12

Calculate the wavelength, in nanometers, of the spectral line produced when an electron in a hydrogen atom undergoes the transition from the energy level n=3 to the level n=1. for this question we assume that equation is set up as E=3 is 1/8hR and E=1 is 1/2hR? because that's how i set up this probl...
by Kandyce Lance 2L
Sun Nov 01, 2020 7:15 pm
Forum: DeBroglie Equation
Topic: wrong equation?
Replies: 4
Views: 29

wrong equation?

I'm not sure if i have this written wrong but i was going through some notes and i noticed i have debroglies equation written as lambda = hc/p but im not sure where the speed of light comes in. does someone mind explaining that?
by Kandyce Lance 2L
Sat Oct 17, 2020 8:44 pm
Forum: Molarity, Solutions, Dilutions
Topic: Photoelectric Effect
Replies: 6
Views: 103

Re: Photoelectric Effect

What was the original metal used in the photoelectric effect? Is that a known fact and is it copper which is why it's used in most of the videos on it, or is copper just a more familiar stand in for the actual metal used?
by Kandyce Lance 2L
Sat Oct 17, 2020 8:36 pm
Forum: General Science Questions
Topic: Rydberg Equation
Replies: 10
Views: 116

Re: Rydberg Equation

In the Atomic Spectra video we had to watch, in the key concepts it says that Rydberg's constant is 3.29x15^15s^-1 but at another point in the video Prof says its 3.29x15^15 Hz. Can someone explain the difference between the units, or why there is no difference? I believe that Hz is a derived SI un...
by Kandyce Lance 2L
Sat Oct 17, 2020 8:32 pm
Forum: Properties of Light
Topic: Frequency vs Wavelength
Replies: 22
Views: 132

Re: Frequency vs Wavelength

I noticed in a previous lecture when prof was going over the equations like E=hv or c=λv the letter "v" was written with a bit of a curve. Is this intentional so we know that this V is referring to frequency and not velocity as it would in other equations, or is that just prof's handwriting?
by Kandyce Lance 2L
Sat Oct 17, 2020 8:27 pm
Forum: General Science Questions
Topic: Kelvin
Replies: 8
Views: 53

Kelvin

When regarding temperature, do we not say something is 273 /degrees /Kelvin, as we would with Celcius and Farenheit? We leave out the "degrees"?
by Kandyce Lance 2L
Sat Oct 17, 2020 8:23 pm
Forum: General Science Questions
Topic: Atomic Spectra
Replies: 3
Views: 583

Re: Atomic Spectra

From the atomic spectra video, the Borh's Constant equation En=hR/n^2, I don't understand why the value of n being a large number would make En a small number. If I were to plug in real number would this concept become more clear?
by Kandyce Lance 2L
Sat Oct 17, 2020 8:04 pm
Forum: General Science Questions
Topic: Rydberg Equation
Replies: 10
Views: 116

Re: Rydberg Equation

In the Atomic Spectra video we had to watch, in the key concepts it says that Rydberg's constant is 3.29x15^15s^-1 but at another point in the video Prof says its 3.29x15^15 Hz. Can someone explain the difference between the units, or why there is no difference?
by Kandyce Lance 2L
Sun Oct 11, 2020 10:26 pm
Forum: Balancing Chemical Reactions
Topic: WK 1 Sapling #10
Replies: 7
Views: 84

Re: WK 1 Sapling #10

I went to a workshop and someone asked this question, and the UA ended up saying that the molar mass should have been given because there would have been no way for us to find it. I ended up pressing the give up button on that one. I was able to find the theoretical yield but couldn't for the life ...
by Kandyce Lance 2L
Sun Oct 11, 2020 10:23 pm
Forum: Balancing Chemical Reactions
Topic: Periodic Table
Replies: 50
Views: 405

Re: Periodic Table

This is just a short anecdote but in sophomore year of high school I tried learning the "Periodic Table Song" by ASAP Science and I still haven't learned the full thing. I know up too 104 before it gets to fast and I can't keep up. T-T I hope one day I can do the whole thing.
by Kandyce Lance 2L
Sun Oct 11, 2020 10:18 pm
Forum: General Science Questions
Topic: Rusty on High School Chem [ENDORSED]
Replies: 200
Views: 141257

Re: Rusty on High School Chem [ENDORSED]

For the people that have utilized the step up sessions and online resources, how helpful are the sessions in comparison to other resources? Is there an overall preference that works for the set up of this class, or would it just depend on the individual.
by Kandyce Lance 2L
Sun Oct 11, 2020 10:12 pm
Forum: Empirical & Molecular Formulas
Topic: Sapling Homework 1 Q#9
Replies: 21
Views: 246

Re: Sapling Homework 1 Q#9

I also had trouble determining how to approach this question, but this thread was very helpful. I think it was really key to understand how to use the grams of products given to find the mass and moles of C, H, and O. From there, the rest of the problem was generally straight forward! I actually ha...
by Kandyce Lance 2L
Sun Oct 11, 2020 10:07 pm
Forum: Administrative Questions and Class Announcements
Topic: Step Up Sessions
Replies: 71
Views: 4370

Re: Step Up Sessions

How do I register or join a step up session online? See my class website at: https://lavelle.chem.ucla.edu/wp-content/supporting-files/Chem14A/Chem14UA_PL_ALL.pdf 40 hours per week. Click on the zoom link for those you want to attend. Organized and Easy :-) Just to clarify, we don't actually have t...

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