Search found 42 matches

by bgiorgi_3A
Tue Nov 24, 2020 9:43 am
Forum: Determining Molecular Shape (VSEPR)
Topic: lone pair e-
Replies: 3
Views: 21

lone pair e-

I have a general question... do lone pair electrons play a role in determining if a molecule is polar or not? When I was in high school someone once told me that if the center atom had lone pairs that then the molecule would be polar, however that does not seem to be the case. For example XeF2 has t...
by bgiorgi_3A
Mon Nov 23, 2020 10:58 am
Forum: Hybridization
Topic: Unhybridized p orbital
Replies: 2
Views: 35

Re: Unhybridized p orbital

Yes, all double bonds involve unhybridized p orbitals. A pi bond is formed when two unhybridized p orbitals from a different atom overlap side by side which results in a shared electron pair which occupies the internuclear axis.
by bgiorgi_3A
Sat Nov 21, 2020 5:13 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: polarity examples
Replies: 5
Views: 46

polarity examples

Hey guys! I was wondering if someone could explain to me why trans-dychloroethene is a nonpolar molecule, but CCl2H2 is a polar molecule? Thank you!
by bgiorgi_3A
Fri Nov 20, 2020 5:14 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: vectors
Replies: 1
Views: 14

vectors

Hey guys! So in lecture, Dr. Lavelle said we would not have to know how to calculate vectors, but it is helpful to have an idea of what the vector looks like when identifying polar molecules. I am personally a bit rusty on vectors and so I was wondering if someone could give me a brief explanation o...
by bgiorgi_3A
Fri Nov 20, 2020 4:15 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Sapling 2E 25
Replies: 2
Views: 19

Sapling 2E 25

2E.25 Draw the Lewis structure and predict whether each of the following molecules is polar or nonpolar: (a) CH2Cl2 (b) CCl4 ; (c) CS2 (d) SF4 Hey guys! I was doing this problem and it said B was polar and D was nonpolar, however I got that B is nonpolar and D is polar. Would someone be able to expl...
by bgiorgi_3A
Fri Nov 20, 2020 9:18 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Lone pairs and 180 degrees
Replies: 1
Views: 23

Lone pairs and 180 degrees

Hey guys! So I am struggling with understanding why the answer to this question is "may be lone pairs." I can't show the diagram here, but it was of a linear molecule with one central atom and two atoms double bonded to it with a 180 degree angle. Could someone please help explain why thei...
by bgiorgi_3A
Mon Nov 16, 2020 2:20 pm
Forum: Electronegativity
Topic: Sapling #20
Replies: 2
Views: 22

Sapling #20

Identify the reasons why oxygen has a lower first ionization energy than both fluorine and nitrogen. select all that apply: 1) oxygen has a smaller atomic radius than fluorine. 2) the 2p electrons in fluorine experience a higher effective nuclear charge than the 2p electrons in oxygen. 3) upon ioniz...
by bgiorgi_3A
Sun Nov 15, 2020 7:03 am
Forum: Coordinate Covalent Bonds
Topic: OH
Replies: 2
Views: 15

OH

Hey guys! Quick question? Is OH a radical? I was doing question 2C.1 and it said OH was not a radical in the answer key.
by bgiorgi_3A
Fri Nov 13, 2020 6:44 am
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: melodie zaki worksheet
Replies: 2
Views: 22

melodie zaki worksheet

Hey guys! I was doing this worksheet and the answer is both c and d. I thought carbon dioxide was a non polar molecule so I was wondering how it has a dipole moment if the dipole moments cancel out? Q2. Generally speaking, molecules with a dipole moment will absorb infrared right, and be classified ...
by bgiorgi_3A
Tue Nov 10, 2020 8:56 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: increasing polarizability
Replies: 5
Views: 26

increasing polarizability

Hey guys! I have a question... if you were to rank N^3-, O^2-, F^-, and Cl^- in order of increasing polarizability, how would you do so?
by bgiorgi_3A
Tue Nov 10, 2020 10:47 am
Forum: Dipole Moments
Topic: melting point
Replies: 4
Views: 22

melting point

Suggest, giving reasons, which substance in each of the following pairs is likely to have the higher normal melting point. C2H5OC2H5 (diethyl ether) or C4H9OH (butanol). Hey guys! So the answer to this is butanol, and I was wondering if the reason was because the structure of butanol is polar wherea...
by bgiorgi_3A
Tue Nov 10, 2020 10:34 am
Forum: Dipole Moments
Topic: Hydrogen bonding
Replies: 2
Views: 12

Hydrogen bonding

Hey guys! I was doing the 3F.5 reading from the textbook and I came across this: "Hydrogen bonding, which occurs when hydrogen atoms are bonded to oxygen, nitrogen, or fluorine atoms, is the strongest type of intermolecular interaction." I thought that ion-ion interactions were the stronge...
by bgiorgi_3A
Mon Nov 09, 2020 1:14 pm
Forum: Lewis Structures
Topic: Riya Shah worksheet wk 6
Replies: 1
Views: 20

Riya Shah worksheet wk 6

Hey guys! So when I did this problem I was asked to draw the lewis structure and find the formal charge of each element. Would you mind walking me through it because for some reason I am doing the wrong amount of bonds in the wrong places.

CNS^-1
by bgiorgi_3A
Wed Nov 04, 2020 10:07 pm
Forum: Resonance Structures
Topic: 2C.17
Replies: 2
Views: 30

2C.17

2C.17 Select from each of the following pairs of Lewis structures the one that is likely to make the dominant contribution to a resonance hybrid. Explain your selection. Hey there! I am unable to post the picture that goes along with this question, but if someone could just explain what the question...
by bgiorgi_3A
Tue Nov 03, 2020 10:55 am
Forum: Ionic & Covalent Bonds
Topic: Electron Affinity
Replies: 5
Views: 40

Electron Affinity

Hey guys! So I was just curious which element has the highest electron affinity in the periodic table because one of my friends and I were debating between F and Cl. Your insight would be appreciated!
by bgiorgi_3A
Tue Nov 03, 2020 10:54 am
Forum: Ionic & Covalent Bonds
Topic: Workshop week 4
Replies: 1
Views: 35

Workshop week 4

Hey guys! So I struggle with Zeff and so I was wondering if someone could help explain the concept a bit and how I would use effective nuclear charge and electron shielding to fill in these blanks. Thanks! b. Outer electrons experience an effective nuclear charge because of electron-electron _______...
by bgiorgi_3A
Tue Nov 03, 2020 10:00 am
Forum: Ionic & Covalent Bonds
Topic: NH4+
Replies: 5
Views: 51

NH4+

Hey guys, so I was writing the electron configuration for NH4+ and I have no problem doing it, but I have just a more unrelated side question about the bonding principles. When I learned about bonding I was taught that H makes 1 bond, O can form 2, N can form 3, and C can form 4. So normally N makes...
by bgiorgi_3A
Mon Nov 02, 2020 4:15 pm
Forum: Ionic & Covalent Bonds
Topic: 2A 17
Replies: 2
Views: 21

2A 17

2A.17 Predict the number of valence electrons present for each of the following ions: (a)Mn4+
Hey guys! For some reason I am struggling super hard with this... would you be able to help me out with A?
by bgiorgi_3A
Mon Nov 02, 2020 11:29 am
Forum: Ionic & Covalent Bonds
Topic: Textbook 2A.1 question
Replies: 4
Views: 34

Re: Textbook 2A.1 question

Hi! I just wanted to weigh in and say if you wrote your electron configuration as [Kr] 4d10 5s2 5p3 then you would be able to see the valence e- easier. Valence e- are the outermost e-. Since Sb has n=5, then you would only look at the electrons that are associated with a coefficient of 5.
by bgiorgi_3A
Sat Oct 31, 2020 10:20 pm
Forum: Ionic & Covalent Bonds
Topic: Strength of bonds
Replies: 13
Views: 65

Re: Strength of bonds

Hi! I just wanted to add that within covalent bonds, single bonds are the weakest bonds and triple bonds are the strongest bonds because they have a stronger hold on the electrons.
by bgiorgi_3A
Thu Oct 29, 2020 8:51 am
Forum: Trends in The Periodic Table
Topic: Electron Affinity
Replies: 10
Views: 40

Re: Electron Affinity

To help determine if something releases or requires energy in relation to electronegativity, I like to think of noble gasses. If you have a noble gas, the octet is complete and so this you would require energy to add an electron because the element is in a stable state. Therefore, for something that...
by bgiorgi_3A
Wed Oct 28, 2020 5:43 pm
Forum: Trends in The Periodic Table
Topic: Trends in Groups 15 and 16
Replies: 4
Views: 36

Trends in Groups 15 and 16

I have a general question about ionization energy. Nitrogen(group 15 element) has a slightly lower ionization energy than oxygen(group 16 element) due to the e- e- repulsion in the 2p orbital. Does the trend of the group 15 element having a slightly lower ionization energy than the group 16 element ...
by bgiorgi_3A
Wed Oct 28, 2020 5:38 pm
Forum: Trends in The Periodic Table
Topic: effective nuclear charge
Replies: 2
Views: 36

effective nuclear charge

Hey there! I was wondering if someone could explain the difference between the nuclear charge of an atom and the effective nuclear charge of an atom to me?
Thank you!
by bgiorgi_3A
Mon Oct 26, 2020 9:59 pm
Forum: DeBroglie Equation
Topic: Diffraction Pattern
Replies: 9
Views: 59

Re: Diffraction Pattern

Hi Lily! I just wanted to add another description of what a diffraction pattern is based on what our lectures covered. Dr. Lavelle talked about throwing pebbles into water and how they make different waves. Think about throwing a handful of rocks into a pond and how the waves would clash with one an...
by bgiorgi_3A
Mon Oct 26, 2020 7:01 pm
Forum: Administrative Questions and Class Announcements
Topic: Locked out of textbook
Replies: 1
Views: 25

Locked out of textbook

Hey guys! Random question, but did any of you get locked out of your online textbooks? I bought a single use code from the UCLA Store, and I've been using the chem textbook at least once a day since school started. For some reason though, it says I do not have access to this textbook and I do not kn...
by bgiorgi_3A
Thu Oct 22, 2020 9:23 am
Forum: Photoelectric Effect
Topic: Work function and incident light
Replies: 3
Views: 34

Re: Work function and incident light

Also could I get some help on the follow up question?
(b) Calculate the wavelength of 1 atom of Rubidium, if it somehow was propelled and is traveling at 5.32 x 10⁴ m/s.
mm Rubidium = 85.468 g/mol
by bgiorgi_3A
Thu Oct 22, 2020 9:09 am
Forum: Photoelectric Effect
Topic: Work function and incident light
Replies: 3
Views: 34

Work function and incident light

Hey guys! I've been having trouble solving this problem. I can get the correct answer (5.4 E-7m) when I use the work function=hv to solve for wavelength, but I didn't use the 1.7x 10^5 m when I solved the problem. How would you recommend solving this? Q8. You have a metal, Rubidium, which has a work...
by bgiorgi_3A
Thu Oct 22, 2020 8:53 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: finding n values
Replies: 3
Views: 31

finding n values

Hey guys! For some reason I'm really struggling with setting up this problem. I thought I knew what I was doing, but I keep getting the answer wrong and so I'm looking for some help! Q7. An electric current is passed through a tube that contains Hydrogen gas. Light is then passed through the prism a...
by bgiorgi_3A
Wed Oct 21, 2020 7:46 am
Forum: Properties of Light
Topic: 1A.3
Replies: 1
Views: 20

1A.3

Hey guys! When I solve this problem, I can get the correct answer (c) by process of elimination, but for some reason I cannot grasp the idea conceptually. Would someone please help me understand? 1A.3 Which of the following happens when the frequency of electromagnetic radiation decreases? Explain y...
by bgiorgi_3A
Tue Oct 20, 2020 8:17 am
Forum: Photoelectric Effect
Topic: Fun with Kinetic Energy
Replies: 2
Views: 26

Fun with Kinetic Energy

Hey chem friends! I am completely lost on this problem and I was wondering if I could get some help setting it up? Thank youuuu! Q7. A particular metal is illuminated by UV photons of wavelength 210 nm and electrons of energy up to 1.25 eV are emitted from the surface. What is the maximum kinetic en...
by bgiorgi_3A
Sun Oct 18, 2020 9:01 pm
Forum: Properties of Light
Topic: Remembering EM spectrum
Replies: 6
Views: 55

Re: Remembering EM spectrum

During office hours this past week we discussed the importance of knowing the general EM spectrum. It is not necessary to know the exact measurement of each region, however you should know that the visible light spectrum is from 400 to 700 nm. I think it is also important to know basic conversions l...
by bgiorgi_3A
Sun Oct 18, 2020 8:56 pm
Forum: Properties of Light
Topic: Chemistry Community Points
Replies: 10
Views: 79

Re: Chemistry Community Points

Hi Ruth! Yes comments count as chemistry community points, as long as they are relevant to what we are learning in class. Hope that helps!
by bgiorgi_3A
Thu Oct 15, 2020 9:59 am
Forum: Photoelectric Effect
Topic: 1B.5
Replies: 2
Views: 41

1B.5

The γ-ray photons emitted by the nuclear decay of a technetium-99 atom used in radiopharmaceuticals have an energy of 140.511 keV. Calculate the wavelength of these γ-rays. Hey guys! I understand how to do this problem, but when I solve it I get a slightly different decimal than the answer in the bo...
by bgiorgi_3A
Thu Oct 15, 2020 9:57 am
Forum: Photoelectric Effect
Topic: 1B 19
Replies: 1
Views: 38

1B 19

Hey guys! I'm looking for help setting up this problem: Protons and neutrons have nearly the same mass. How different are their wavelengths? Calculate the wavelength of each particle when traveling at 2.75 × 10 5 m ⋅ s − 1 in a particle accelerator and report the difference as a percentage of the wa...
by bgiorgi_3A
Wed Oct 14, 2020 5:04 pm
Forum: Properties of Light
Topic: atomic spectrum fun
Replies: 4
Views: 51

atomic spectrum fun

Hey guys! Quick question- whenever you are calculating questions regarding the atomic spectra and you get v in negative units, you change the sign to be positive correct? For example: Calculate the frequency of a photon emitted by a hydrogen atom when an electron makes a transition from the fourth t...
by bgiorgi_3A
Tue Oct 13, 2020 9:18 pm
Forum: Properties of Light
Topic: Finding kinetic energy
Replies: 3
Views: 64

Finding kinetic energy

Hey guys! So lately I've been understanding the material, but whenever I do a problem using the Kinetic Energy = [.5 (m)(v)^2] I can never get the right answer. For example in 1.B.3- this example is given: Suppose you are developing a radiation detector to be used on a spacecraft and decide to use a...
by bgiorgi_3A
Fri Oct 09, 2020 7:04 pm
Forum: Molarity, Solutions, Dilutions
Topic: G.13
Replies: 3
Views: 55

Re: G.13

Hi Farah! I'm sure you probably understand how to do the calculations by now, but I just wanted to recommend drawing a diagram. When I got stuck on this problem, I drew a tiny beaker and buret to help me visualize what I was actually doing. I recommend drawing out concepts if you are ever completely...
by bgiorgi_3A
Fri Oct 09, 2020 7:00 pm
Forum: Molarity, Solutions, Dilutions
Topic: Fundamentals G, Question 5: Molarity Question, Significant Figures
Replies: 2
Views: 38

Re: Fundamentals G, Question 5: Molarity Question, Significant Figures

Often it is recommended to do as much of your calculations as possible without rounding. This allows you to get the most precise answer to round from at the end of a calculation. That's when I would recommend applying your sigfig rules.
by bgiorgi_3A
Thu Oct 08, 2020 2:52 pm
Forum: SI Units, Unit Conversions
Topic: E 29
Replies: 2
Views: 51

E 29

Hey chem friends! I'm looking for help on part d of E.29. A chemist measured out 8.61g of copper(II) chloride tetra hydrate CuCl2(4H2O) d) what fraction of the total mass of the sample is due to oxygen? I have no problem finding the answer, I was just curious why the textbook reports the answer in 4...
by bgiorgi_3A
Wed Oct 07, 2020 6:53 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Chemical Formulas of Compounds
Replies: 9
Views: 87

Re: Chemical Formulas of Compounds

Based off of the last lecture I think it is important to know that water and carbon dioxide are produced when combustion occurs. Other than that you probably do not need to know all compounds by memory.
by bgiorgi_3A
Tue Oct 06, 2020 8:17 pm
Forum: Molarity, Solutions, Dilutions
Topic: Fundamentals G. 5
Replies: 2
Views: 52

Re: Fundamentals G. 5

Hey! First off to help out with this problem, it is important to note that the question asks for a) and b) in mmol which is where you add a x10^-3. In this problem you are given the grams of sodium carbonate and a volume in mL. Your first step would be to divide 2.111g by the molar mass of sodium ca...
by bgiorgi_3A
Tue Oct 06, 2020 8:48 am
Forum: Administrative Questions and Class Announcements
Topic: Advice from a Medical Student [ENDORSED]
Replies: 221
Views: 116067

Re: Advice from a Medical Student [ENDORSED]

Thank you so much for giving such helpful tips! I was nervous heading into this course, but with what you say about Dr. Lavelle, I am certain I will be prepared for my future career after completing Chem 14A and B. Quick question... did you also save every practice problem you did outside of lecture...

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