Search found 45 matches

Wed Nov 25, 2020 8:28 pm
Forum: Hybridization
Topic: answer not displayed for 2.57
Replies: 1
Views: 23

For some reason the answer booklet does not include 2.57 's answer. Does anyone have the answer to 2.57, specifically the 2 pi-bond hybridizations for Nitrogen? (C triple bonded to nitrogen, nitrogen has a lone pair).
Wed Nov 25, 2020 7:51 pm
Forum: Hybridization
Topic: 2F.15 textbook problem
Replies: 2
Views: 22

Re: 2F.15 textbook problem

[quote="Using the same approach sp2 would have 1/3 or 33.3% s-character. A sp3 hybridized atom with 25% s-character has the bond angle of 109.5 degrees. A sp2 hybridized atom with 33.3% s-character (a great s-character) has the bond angle of 120 degrees (greater bond angle). " [/quote] i j...
Tue Nov 24, 2020 11:02 pm
Forum: Administrative Questions and Class Announcements
Topic: Final exam (fall 2020 quarter)
Replies: 11
Views: 75

Re: Final exam (fall 2020 quarter)

The final will be cumulative, so it will have everything we've learned. What I am curious is the percentage of material covered (will there be an emphasis on week 7+ OR an equal amount of everything).
Tue Nov 24, 2020 11:00 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: axial vs. equatorial
Replies: 5
Views: 39

axial vs. equatorial

can someone please explain why minimizing the 90 degrees repulsions is ideal, so that lone pairs occupy the equatorial positions? Is it to keep the molecule as compacted as possible? To keep the molecule together?
Tue Nov 24, 2020 10:50 pm
Forum: Dipole Moments
Topic: 2E #29
Replies: 7
Views: 18

Re: 2E #29

polarity is intricately tied with electronegativity and dipole moment is (in this example) tied with the positioning of the Cl. Think cis- and trans- molecules in this scenario. The largest dipole moment would come from the Cl atom whose dipole moments do not cancel, b and c both cancel because the ...
Tue Nov 24, 2020 10:42 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 2E #19b
Replies: 1
Views: 13

Re: 2E #19b

I think in this case you would consider both Be and C in your thinking process. For example, actively noticing that Be is going to be in a linear structure with 2C's and that the 2C's are going to be in a tetrahedral structure with the H's. This way you can show your full understanding of the molecu...
Tue Nov 24, 2020 10:38 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 2E.7
Replies: 3
Views: 14

Re: 2E.7

Please correct me if I am wrong, but I believe the size of the atom do not factor into the bond angle.
Sun Nov 22, 2020 9:07 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: memorizing VSEPR models
Replies: 13
Views: 48

memorizing VSEPR models

I have a hard time memorizing and visualizing trigonal pyramidal, seesaw, and trigonal bipyramidal. Can someone show me how you memorized them/what seems to work? Thanks so much!
Sun Nov 22, 2020 9:01 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Sapling #10
Replies: 5
Views: 22

Re: Sapling #10

Hi! since the carbon atom is the central atom and oxygen is double bonded to carbon, that leaves two fluorine atoms at a 120 degree position from each other. Like the above posts said, the electronegativities of both are very high but both are fluorine atoms so they are equally strong in electronega...
Sun Nov 22, 2020 8:58 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Textbook Problem 2E. 19
Replies: 3
Views: 16

Re: Textbook Problem 2E. 19

(a) the thiosulfate ion, S2O32−; (b) (CH3)2Be; (c) BH2−; (d) SnCl2

for part b I like to think of it almost like 2 CH3's sandwiching the Be. So the central atom would be Be because of its low ionization energy. For part c Boron would be the central atom, and for part d Sn would be the central atom.
Sun Nov 22, 2020 8:54 pm
Forum: Hybridization
Topic: Sapling#11
Replies: 6
Views: 25

Re: Sapling#11

Hi!
sp^3 would mean that s (1 orbital) and p^3 (3 orbitals) which corresponds to the 3 bonded pairs + 1 lone pair.
Thu Nov 19, 2020 5:31 pm
Forum: Octet Exceptions
Replies: 4
Views: 23

the hypochlorite ion (ClO-) is covalently bonded, with the oxygen having a formal charge of -1.
Sun Nov 15, 2020 6:31 pm
Forum: Lewis Structures
Topic: VSEPR
Replies: 4
Views: 21

Re: VSEPR

Since our last lecture that need be covered on the midterm was Wednesday, I don't think VESPER will be required on the midterm. I like to think that if you know it it kind of helps you understand the structure in your head better, so it doesn't hurt to learn about VESPER now.
Sun Nov 15, 2020 6:28 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm 2 format?
Replies: 9
Views: 45

Re: Midterm 2 format?

I attended a step up session and heard that there will be around 25 questions so the the general consensus is that there will be less point weight to each.
Fri Nov 13, 2020 12:23 am
Forum: Ionic & Covalent Bonds
Topic: Bond Character
Replies: 6
Views: 39

Re: Bond Character

they describe properties of the chemical. For example, the metals usually have low ionization energies. The post above mentioned metallic character, and that is quantifying how reactive a metal is.
Fri Nov 13, 2020 12:17 am
Forum: Resonance Structures
Topic: Resonance structures contribution to overall structure
Replies: 4
Views: 17

Re: Resonance structures contribution to overall structure

the structure that contributes the least to the overall structure is one that has the highest energy. Or the most unstable one. This can be the form of the least amount of covalent bonds, the most amount of formal charges, or one that does not apply the ideal "octet rule"
Fri Nov 13, 2020 12:10 am
Forum: Coordinate Covalent Bonds
Topic: Hydrogen bonding
Replies: 12
Views: 60

Re: Hydrogen bonding

hydrogen bond is using attractions of varying levels of electronegativity to make bonds, so it is different from a coordinate covalent bond.
Wed Nov 04, 2020 8:45 pm
Forum: Octet Exceptions
Replies: 5
Views: 35

Jessica Katz 1G wrote: The radicals can damage DNA when they react with it and food supplements that we ingest can also react with radicals but that would be before any damage is caused.
Are you referring to oxidation when you say that "they react with it"?
Wed Nov 04, 2020 8:29 pm
Forum: Resonance Structures
Replies: 1
Views: 18

This hypothetical situation would not be a resonance because the electrons are still delocalized, like you said.
Wed Nov 04, 2020 8:21 pm
Forum: Lewis Structures
Topic: Kelter Method
Replies: 2
Views: 17

Re: Kelter Method

Just to go over what the Kelter Method is... first you look at the name of the compound and find the number of electrons there should be. Then you multiply the number of electrons that would complete the octet rule (if we have CO3 -2) then it would be 4x8 =32 electrons. You then substract the initia...
Wed Nov 04, 2020 8:11 pm
Forum: Lewis Structures
Topic: Lewis Structure
Replies: 7
Views: 46

Re: Lewis Structure

mlouie_1I wrote: If you are still unsure, you could compare the formal charge when the atoms are placed differently.

what do you mean by comparing the formal charge when the atoms are placed differently?
Wed Nov 04, 2020 8:06 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Textbook question 1E 21
Replies: 3
Views: 27

Re: Textbook question 1E 21

Yes, the number of unpaired electrons is however many electrons that have only one electron in that orbital.
Sat Oct 31, 2020 11:21 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Shape of Orbitals
Replies: 8
Views: 43

Re: Shape of Orbitals

The shape of the orbitals is the probable area that the electrons can be found in, and the equation that corresponds to this portrayal is the schrodinger equation and the schrodinger equation squared.
Sat Oct 31, 2020 11:11 am
Forum: Ionic & Covalent Bonds
Topic: Salt
Replies: 4
Views: 33

Re: Salt

Going off of what we know about salt, a salt consists of the positive ion (cation) of a base and the negative ion (anion) of an acid. Since we know that ammonium is a cation and sulfate is an anion, we know that ammonium sulfate is a salt.
Sat Oct 31, 2020 11:07 am
Forum: Student Social/Study Group
Topic: Test Scored for Midterm 1
Replies: 49
Views: 345

Re: Test Scored for Midterm 1

I asked my TA after the test on zoom, and she said it takes some time to sort the questions out since there are different versions and partial credit, like the above post said, so it will probably come out next week.
Sat Oct 31, 2020 11:03 am
Forum: Trends in The Periodic Table
Topic: Periodic Table & Electron Affinity
Replies: 11
Views: 45

Re: Periodic Table & Electron Affinity

electron affinity is the energy that gets released when an electron has been added to the atom, undergoing an exothermic process. Like the above posts had said, the affinity increases across the period and decreases down the group, similarly to the ionization energy.
Sat Oct 31, 2020 10:58 am
Forum: Student Social/Study Group
Topic: How to relax
Replies: 97
Views: 377

Re: How to relax

I usually like to do my puzzle and browse on amazon for fun!
Sat Oct 24, 2020 9:49 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Confusion on Experimental Data Graph
Replies: 1
Views: 21

Re: Confusion on Experimental Data Graph

What you are saying is correct, as the n-level is increasing then the difference or "gap" should become smaller and smaller. Could it be that the variable shown in the image is wavelength and the other refers to the energy?
Thu Oct 22, 2020 10:16 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Sapling Weeks 2-4 #11
Replies: 2
Views: 31

Re: Sapling Weeks 2-4 #11

So the n corresponds to the principal quantum number and the l corresponds to the angular momentum quantum number. In this case, I would just start looking at the leading coefficient for n. For l, I would recall the sequence of s, p, d, f and then s's l = 0, p's l = 1, and so on.
Wed Oct 21, 2020 11:31 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: missing question?
Replies: 1
Views: 47

missing question?

Does anyone's textbook shows a part b of 2E.3? Mine just shows .
This is what I see:
2E.3 Draw the structures and name the shapes of the following molecules: (a) HCN; (b) .
Wed Oct 21, 2020 11:24 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Midterm 1
Replies: 18
Views: 190

Re: Midterm 1

I think no one knows for sure if there's going to be more than one question on it until we take the exam. For me at least, it seems to be remembering the formula and then know when to use the components of the equation in the context of the word problem!
Tue Oct 20, 2020 2:19 pm
Forum: Ionic & Covalent Bonds
Topic: 2A23 Part E
Replies: 4
Views: 67

Re: 2A23 Part E

Yes, in this case although you would count normally forward to Radon and have Bismuth have the charge 3-, since it is denoted (III), it counts as 3+ and thus 3 F charges would cancel out. The answer would be BiF3
Fri Oct 16, 2020 10:35 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm Multiple Choice Format
Replies: 6
Views: 75

Re: Midterm Multiple Choice Format

Interesting, I recall my TA mentioning the partial credit as well because "partial credit will be given if the number of sig figs are off". If it's all multiple choice, I don't know how that would work.
Fri Oct 16, 2020 10:30 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Rydberg Equation
Replies: 7
Views: 43

Re: Rydberg Equation

The Rydberg equation is
1/lambda = R (1/n^2(final) - 1/n^2 (initial))
Fri Oct 16, 2020 10:27 pm
Forum: Ionic & Covalent Bonds
Topic: Bond Forming
Replies: 8
Views: 204

Re: Bond Forming

I vaguely recall that weaker forces such as the Van der Waals forces allows small, miniscule interactions that would allow bonds to form simultaneously. Otherwise, like above posts have said, the strong bonds need a certain activation energy and supplied energy to form bonds.
Fri Oct 16, 2020 10:27 pm
Forum: Ionic & Covalent Bonds
Topic: Bond Forming
Replies: 8
Views: 204

Re: Bond Forming

I vaguely recall that weaker forces such as the Van der Waals forces allows small, miniscule interactions that would allow bonds to form simultaneously. Otherwise, like above posts have said, the strong bonds need a certain activation energy and supplied energy to form bonds.
Thu Oct 15, 2020 1:36 pm
Forum: Quantum Numbers and The H-Atom
Topic: Writing Electron Configurations 1E.23
Replies: 5
Views: 45

Re: Writing Electron Configurations 1E.23

I think you would usually put 3d after 4s because when you follow the lines on the electron configuration chart, 3d comes after 4s. Are you referring to the slanted arrows displaying the configurations? I would rank them based on principal quantum numbers, so in increasing leading quantum numbers b...
Thu Oct 15, 2020 1:11 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Textbook Problem 1A.15
Replies: 2
Views: 36

Re: Textbook Problem 1A.15

Could someone help me with this problem: 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. Thanks! Since the line is observ...
Thu Oct 15, 2020 12:31 pm
Forum: Properties of Light
Topic: Intensity v Energy
Replies: 18
Views: 134

Re: Intensity v Energy

The incoming ray's intensity is its number of photons in a specific amount of area and the energy of the incoming ray is its electromagnetic radiation being in the form of frequency and wavelength. When increasing the light intensity, the number of individual photons is increased; the energy of thes...
Sun Oct 11, 2020 11:59 pm
Forum: Significant Figures
Topic: Easy 3 Rules
Replies: 9
Views: 108

Re: Easy 3 Rules

Thank you for this!
Thu Oct 08, 2020 12:21 pm
Forum: Administrative Questions and Class Announcements
Topic: Accessing the E-textbook [ENDORSED]
Replies: 58
Views: 6360

Re: Accessing the E-textbook[ENDORSED]

For anyone who ordered their textbook from the UCLA store and already received it, was it a physical copy? and if so, did it include an access code for sapling and/or the e-book? A student said that they have received an email with a picture of the access code, and she said to check your junk folde...
Wed Oct 07, 2020 2:01 pm
Forum: Balancing Chemical Reactions
Topic: Combustion Products
Replies: 13
Views: 66

Re: Combustion Products

In a chemically balanced equation, you will need to balance your equation to yield the correct and corresponding moles of H2O and CO2. Combustion is just like any other chemical equation, except we know the products here.
Wed Oct 07, 2020 1:49 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Heisenberg Uncertainty Principle Post-Mod Q
Replies: 2
Views: 37

Re: Heisenberg Uncertainty Principle Post-Mod Q

Given the Heisenberg uncertainty principle formula, delta Px * Delta x >= h/(4pi), we can deduct the following: uncertainty in momentum of particle in the x-direction is velocity of particle in the x-direction multiplied by the mass (9.1*10^-31) h is a constant and delta x is given. so once you find...
Wed Oct 07, 2020 12:22 pm
Forum: Limiting Reactant Calculations
Topic: Sapling Homework Question 10
Replies: 16
Views: 224

Re: Sapling Homework Question 10

The first thing I did was figure out the molecular formulas or 2butone and 3 methyl. Every like "point" or "corner" is a carbon molecule. Every carbon molecule forms 4 bonds. So we have to imagine there are hydrogen molecules attached to each carbon to fulfill these 4 bonds. So ...
Wed Oct 07, 2020 12:03 pm
Forum: Administrative Questions and Class Announcements
Topic: Step Up Sessions
Replies: 71
Views: 4401

Re: Step Up Sessions

Regarding step up sessions, do all UAs share the same worksheet or is it recommended to attend multiple sessions because they all focus on different concepts? For the step-up sessions I attended, one UA gave us a worksheet to work on but then also he gave us some past midterm problems to work on at...