Search found 17203 matches

by Chem_Mod
Mon Jul 22, 2019 5:43 pm
Forum: Lewis Structures
Topic: Complete Lewis Structure [ENDORSED]
Replies: 6
Views: 170

Re: Complete Lewis Structure [ENDORSED]

However, if the species in question is charged, such as SO4^-2, do make sure to include the negative charge in your drawing (recall from lecture, we wrote the -2 charge on the upper right of the Lewis structure outside of the brackets enclosing the drawing)
by Chem_Mod
Mon Jul 22, 2019 5:40 pm
Forum: Resonance Structures
Topic: Resonance Hybrid
Replies: 3
Views: 148

Re: Resonance Hybrid

You should be able to draw all equivalent resonance structures; you will not need to draw the resonance hybrid itself, but you should know that it is a blend of all the resonance structures and how that affects the bond lengths.
by Chem_Mod
Mon Jul 22, 2019 12:29 pm
Forum: Ionic & Covalent Bonds
Topic: Polarizing Power [ENDORSED]
Replies: 2
Views: 109

Re: Polarizing Power [ENDORSED]

The above Q and A was slightly edited for clarification.

Fe3+ has higher charge and therefore higher polarizing power compared to Mg2+.
Higher the charge typically results in higher polarizing power, dominating the difference in size (which is another factor considered in polarizing power).
by Chem_Mod
Mon Jul 22, 2019 12:13 pm
Forum: Hybridization
Topic: Electrons
Replies: 3
Views: 110

Re: Electrons

For an electron to be promoted, it means that the electron is being excited and moved to the next higher orbital.
by Chem_Mod
Mon Jul 22, 2019 12:12 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Shape of Molecules and Strength of Interaction
Replies: 1
Views: 69

Re: Shape of Molecules and Strength of Interaction

The intermolecular forces of attraction (like London dispersion forces) between spherical shaped molecules is less because of smaller surface area which makes it weaker and more reactive as compared to the rod-shaped one which has a larger surface area, thus having a stronger intermolecular force be...
by Chem_Mod
Mon Jul 22, 2019 11:46 am
Forum: Dipole Moments
Topic: Dipole
Replies: 1
Views: 68

Re: Dipole

Dipole moments occur in most molecules, whether it is linear or not. A dipole moment occurs within a molecule, and determines where the e- density is greatest (towards the more electronegative atom). For example, in water (which is not linear), the electrons tend to be drawn closer to the oxygen, gi...
by Chem_Mod
Mon Jul 22, 2019 11:39 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 1
Views: 68

Re: Bond Angles

There are not fixed angles, because it all depends on the different elements that are bound to the central atom (or whether there are lone pairs), which create different electron repulsions. If all the atoms attached are the same (i.e. CH4), then the angles would be the same, but the angles vary bet...
by Chem_Mod
Mon Jul 22, 2019 10:48 am
Forum: Octet Exceptions
Topic: Expanded Octet Exception
Replies: 1
Views: 77

Re: Expanded Octet Exception

It varies between atoms as to how many it could hold. You can consider the phosphorous's hybridization state when it is excited, it can fill up the d-orbital, but it only has 5 electrons in its outer shell that can bind with other atoms (recall its electron configuration: 3s2p3). It will only be abl...
by Chem_Mod
Sun Jul 21, 2019 10:01 pm
Forum: Hybridization
Topic: Hybridization
Replies: 1
Views: 59

Re: Hybridization

As I explained in class. The hybridization model is needed to obtain the correct bonding and shape. I went through CH 4 as an example. C has only two unpaired electrons and therefore would form two covalent bonds. Yet it forms four bonds which one can show with four sp 3 hybrid orbitals each with on...
by Chem_Mod
Sun Jul 21, 2019 12:36 am
Forum: Administrative Questions and Class Announcements
Topic: Michelle's Weekly Worksheets
Replies: 9
Views: 342

Re: Michelle's Weekly Worksheets

Week 4 answer key:
Week 4 Workshop Key.docx
(18.1 KiB) Downloaded 11 times
by Chem_Mod
Sat Jul 20, 2019 8:43 pm
Forum: Administrative Questions and Class Announcements
Topic: Week 4 Worksheet Answers
Replies: 1
Views: 45

Week 4 Worksheet Answers

Here are the Week 4 Worksheet Answers.
by Chem_Mod
Sat Jul 20, 2019 5:57 pm
Forum: Sigma & Pi Bonds
Topic: Hybrid Orbitals [ENDORSED]
Replies: 1
Views: 70

Re: Hybrid Orbitals [ENDORSED]

As I explained in class. The hybridization model is needed to obtain the correct bonding and shape. I went through CH 4 as an example. C has only two unpaired electrons and therefore would form two covalent bonds. Yet it forms four bonds which one can show with four sp 3 hybrid orbitals each with on...
by Chem_Mod
Sat Jul 20, 2019 4:53 pm
Forum: Administrative Questions and Class Announcements
Topic: ASHLEY'S STEP UP WORKSHEETS
Replies: 15
Views: 512

Re: ASHLEY'S STEP UP WORKSHEETS

Step up worksheet for this Monday
by Chem_Mod
Sat Jul 20, 2019 4:52 pm
Forum: Administrative Questions and Class Announcements
Topic: ASHLEY'S STEP UP WORKSHEETS
Replies: 15
Views: 512

Re: ASHLEY'S STEP UP WORKSHEETS

Good catch! Yes you are right, CO2 would have more ionic character. C and S have very similar electronegativity, so CS2 would be more covalent.
by Chem_Mod
Sat Jul 20, 2019 12:11 pm
Forum: Lewis Structures
Topic: 3.57 6th edition part B
Replies: 1
Views: 116

Re: 3.57 6th edition part B

Please post the full question. Don't have 6th edition on me.
by Chem_Mod
Fri Jul 19, 2019 1:01 pm
Forum: Student Social/Study Group
Topic: Test 2
Replies: 1
Views: 154

Re: Test 2

Hopefully this worked out.
by Chem_Mod
Fri Jul 19, 2019 12:59 pm
Forum: Ionic & Covalent Bonds
Topic: CX and CN bonds [ENDORSED]
Replies: 2
Views: 124

Re: CX and CN bonds [ENDORSED]

Draw the Lewis structure for CN and you will see it is a C triple bond to N.

As I discussed in class:
CC single bond is weaker/longer
CC double bond is stronger/shorter
CC triple bond is strongest/shortest

What do you mean by CX bonds?
by Chem_Mod
Fri Jul 19, 2019 8:45 am
Forum: Determining Molecular Shape (VSEPR)
Topic: definition
Replies: 2
Views: 140

Re: definition

That refers to the angle we would see using the bonds of among those 3 elements.
by Chem_Mod
Thu Jul 18, 2019 11:00 pm
Forum: Dipole Moments
Topic: Dipoles N, O, and F, etc.
Replies: 3
Views: 86

Re: Dipoles N, O, and F, etc.

The bond between the electronegative atoms does have a dipole moment. However, depending on the shape of the molecule, as a whole, it can either be polar (when dipole moments do not cancel out each other) or nonpolar (when dipole moments cancel out each other). H-Cl is a polar molecule because of th...
by Chem_Mod
Wed Jul 17, 2019 11:45 pm
Forum: Ionic & Covalent Bonds
Topic: Number of valence electrons - including d electrons [ENDORSED]
Replies: 1
Views: 126

Re: Number of valence electrons - including d electrons [ENDORSED]

Your answer is correct: Depends on whether the element is in the d block or the p block. If in the d block (i.e, with an incomplete d shell), count the s- and d-electrons. If in the p block, count only the s- and p-electrons. This is typically not a question I ask. Our bonding focus is the p-block a...
by Chem_Mod
Wed Jul 17, 2019 11:23 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: difference between linear and bent, or v-shape
Replies: 1
Views: 114

Re: difference between linear and bent, or v-shape

Based on VSEPR geometries, if the central atom has three pairs of electrons, the molecule is linear (it must also have two noncentral atoms). The formal charge of I (central atom) is -1 so that is where the charge comes from in I3^-1. I can break the octet rule and hold more electrons since it has d...
by Chem_Mod
Wed Jul 17, 2019 11:04 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: difference between structure
Replies: 1
Views: 103

Re: difference between structure

Trigonal bipyramidal shapes and seesaw shapes have the same number of regions of electron density: 5. For example, PCl5 and SF4 both have the electron shape of trigonal bipyramidal as they both have 5 regions of electron density. However, PCl5 has no lone pairs and SF4 does have one lone pair. This ...
by Chem_Mod
Wed Jul 17, 2019 7:28 pm
Forum: Administrative Questions and Class Announcements
Topic: ASHLEY'S STEP UP WORKSHEETS
Replies: 15
Views: 512

Re: ASHLEY'S STEP UP WORKSHEETS

Answers to the last worksheet
by Chem_Mod
Wed Jul 17, 2019 10:50 am
Forum: Administrative Questions and Class Announcements
Topic: Michelle's Weekly Worksheets
Replies: 9
Views: 342

Re: Michelle's Weekly Worksheets

Week 4 handout for this Thursday's workshop!
Week 4 Workshop (1) (1).docx
(14.84 KiB) Downloaded 19 times
by Chem_Mod
Wed Jul 17, 2019 10:36 am
Forum: Administrative Questions and Class Announcements
Topic: JONATHAN'S WEEKLY WORKSHEETS
Replies: 2
Views: 206

Re: JONATHAN'S WEEKLY WORKSHEETS

Here is my week 4 workshop worksheet. We will go through this in my session. Thank you!
by Chem_Mod
Wed Jul 17, 2019 10:11 am
Forum: Lewis Structures
Topic: Molecule Formulas
Replies: 3
Views: 127

Re: Molecule Formulas

Molecular formulas will generally be given on exams unless a question refers to a simpler compound such as HCl (hydrochloric acid). However, you should be familiar with common, simple molecular formulas.
by Chem_Mod
Wed Jul 17, 2019 10:09 am
Forum: Ionic & Covalent Bonds
Topic: Intermolecular farces
Replies: 2
Views: 111

Re: Intermolecular farces

Both CO2 and N2 are nonpolar molecules. The molecular shape of CO2 and N2 is linear. There is no dipole moment for N2 since there is no difference in electronegativity between the two Ns. There is a difference in electronegativity between C and O but those dipole moments cancel each other out since ...
by Chem_Mod
Wed Jul 17, 2019 10:03 am
Forum: Ionic & Covalent Bonds
Topic: Order of electron loss in ion formation
Replies: 4
Views: 121

Re: Order of electron loss in ion formation

I believe you are referring to the 3d/4s orbital exception. Electrons in the 4s energy level are lost first because electrons lost first will come from the highest energy level. The 4s orbital is higher in energy than the 3d orbital.
by Chem_Mod
Tue Jul 16, 2019 7:19 pm
Forum: Ionic & Covalent Bonds
Topic: 3.51 6th Ed.
Replies: 2
Views: 104

Re: 3.51 6th Ed.

Structures that do not have charges (neutral) are considered more stable. Although chlorine may be more electronegative than oxygen, it is still more favorable to have O as the central atom in the structure based on formal charge. Chlorine is also not that much less electrongative than oxygen.
by Chem_Mod
Tue Jul 16, 2019 7:14 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Energy State
Replies: 2
Views: 87

Re: Energy State

An excited state describes an atom in which the total energy of the electrons can be lowered by transferring one or more electrons to different orbitals. For an excited state atom, not all the electrons are in the lowest possible energy levels.
by Chem_Mod
Tue Jul 16, 2019 2:05 pm
Forum: Administrative Questions and Class Announcements
Topic: Week 4 Worksheet
Replies: 1
Views: 104

Week 4 Worksheet

Here is the Week 4 Worksheet. Answers will be posted tomorrow.
by Chem_Mod
Tue Jul 16, 2019 1:39 pm
Forum: Dipole Moments
Topic: Charges
Replies: 1
Views: 89

Re: Charges

Dipole moments occur when there is a separation of charge and arise from differences in electronegativity. When two electrical charges of opposite sign and magnitude are separated by a distance, an electric dipole is established. The size of a dipole is measured by the dipole moment, measured in deb...
by Chem_Mod
Tue Jul 16, 2019 1:33 pm
Forum: Hybridization
Topic: hybridization
Replies: 2
Views: 90

Re: hybridization

The number of hybrid orbitals is determined by the regions of electron density. For example, in C2H4, each C has three regions of electron density so we need three hybrid orbitals. Three sp2 hybrid orbitals form 3 sigma bonds on each C: one C2sp2—C2sp2, and two H1s—C2sp2. The unhybridized 2p orbital...
by Chem_Mod
Tue Jul 16, 2019 1:28 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polarity
Replies: 1
Views: 82

Re: Polarity

To determine polarity of a molecule: A polar molecule must have polar bonds with dipoles that do not cancel. A non-polar molecule must have zero electric dipole moment, which is possible if it contains nonpolar bonds or polar bonds with dipoles that cancel. To determine polarity of a bond: The polar...
by Chem_Mod
Tue Jul 16, 2019 9:32 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Midterm Question 5C
Replies: 1
Views: 63

Re: Midterm Question 5C

First write the ground state configuration for neutral Cu. That would give you [Ar]3d^(10)4s^(1). *Remember that Cu transfers a 4s electron to its 3d orbital because a full 3d orbital gives it more stability). To get Cu+, remove one electron. The electron in the highest energy level is the 4s, so we...
by Chem_Mod
Tue Jul 16, 2019 9:30 am
Forum: Bond Lengths & Energies
Topic: boiling and melting points
Replies: 1
Views: 68

Re: boiling and melting points

A larger molecule will in general have more electrons, meaning the dispersion forces between its molecules will be stronger. This will raise both its melting and boiling points. However, substances that experience stronger intermolecular forces will have higher melting points than those that only ex...
by Chem_Mod
Tue Jul 16, 2019 9:16 am
Forum: Administrative Questions and Class Announcements
Topic: Homework
Replies: 1
Views: 83

Re: Homework

Homework from either or both sections is fine as I cover both this week in class.
by Chem_Mod
Tue Jul 16, 2019 12:22 am
Forum: Ionic & Covalent Bonds
Topic: What to do if electronegativity difference is between 1.5 and 2? [ENDORSED]
Replies: 3
Views: 105

Re: What to do if electronegativity difference is between 1.5 and 2? [ENDORSED]

I said if the difference is between 2 and 1.5 then one needs to study the properties of that specific compound to determine if it has properties of a salt or a molecule. Something that we would not do as this is not a lab course.
by Chem_Mod
Tue Jul 16, 2019 12:18 am
Forum: Resonance Structures
Topic: Test 2
Replies: 1
Views: 65

Re: Test 2

no
by Chem_Mod
Mon Jul 15, 2019 12:31 pm
Forum: Ionic & Covalent Bonds
Topic: Ground State
Replies: 13
Views: 207

Re: Ground State

In general, half filled d shells and fully filled d shells are typically preferred (ie slightly more stable). Some atoms will transfer the electrons, some won't, especially the heavier elements. It is mostly a case by case basis
by Chem_Mod
Mon Jul 15, 2019 12:29 pm
Forum: Ionic & Covalent Bonds
Topic: Radicals
Replies: 7
Views: 190

Re: Radicals

You can figure out if a single atom is a radical by writing out the electron configuration. For molecules, if any molecule has an odd number of electrons (uneven number), then it is likely a radical as there must be an unpaired electron on that molecule. However there are molecules that have two unp...
by Chem_Mod
Mon Jul 15, 2019 12:26 pm
Forum: Electronegativity
Topic: Radius and energy levels
Replies: 1
Views: 95

Re: Radius and energy levels

The Rydberg equation relates n (energy of the shell) to the energy of the electron in that shell, but there isn't an equation that directly relates the energy of the electron to the radius of the nucleus (i.e. the size of the atom) Interesting question though! Maybe you can go on and discover that e...
by Chem_Mod
Mon Jul 15, 2019 12:20 pm
Forum: Ionic & Covalent Bonds
Topic: Covalent Bonds [ENDORSED]
Replies: 3
Views: 122

Re: Covalent Bonds [ENDORSED]

Yes, covalent bonds refer to the types of bonds where electrons are shared; they can be either polar or nonpolar covalent bonds. Polar covalent bonds are a type of covalent bond where the electrons are not equally shared as described above (nonpolar covalent bonds occur where electrons are equally o...
by Chem_Mod
Mon Jul 15, 2019 12:11 pm
Forum: Administrative Questions and Class Announcements
Topic: Test #2
Replies: 2
Views: 89

Re: Test #2

Test 2 will cover all the material listed here: https://lavelle.chem.ucla.edu/wp-conten ... _Bonds.pdf
by Chem_Mod
Mon Jul 15, 2019 12:11 pm
Forum: Lewis Structures
Topic: Formal Charge [ENDORSED]
Replies: 2
Views: 93

Re: Formal Charge [ENDORSED]

Yes, you could draw a structure with atoms containing formal charge greater than 2, but this would not be a very good representation of the true structure, as greater formal charge in either direction (positive or negative) makes the structure less stable. Neutral is most stable as said above
by Chem_Mod
Mon Jul 15, 2019 12:09 pm
Forum: Ionic & Covalent Bonds
Topic: What to do if electronegativity difference is between 1.5 and 2? [ENDORSED]
Replies: 3
Views: 105

Re: What to do if electronegativity difference is between 1.5 and 2? [ENDORSED]

In addition, salts are found in groups 1 and 2 of the periodic table (ie Na+ and Mg(2+)
by Chem_Mod
Sun Jul 14, 2019 11:58 am
Forum: Bond Lengths & Energies
Topic: Electrostatic Potential Energy Formula
Replies: 2
Views: 77

Re: Electrostatic Potential Energy Formula

That equation represents the level of electrostatic attraction.
by Chem_Mod
Sun Jul 14, 2019 11:55 am
Forum: Ionic & Covalent Bonds
Topic: Cutoff Values
Replies: 1
Views: 77

Re: Cutoff Values

The cutoff factors were discussed in lecture and should be in the book as I do not have the exact numbers on me. However the important concept is that bonds are not totally ionic or totally covalent, and is instead a spectrum. Remember there is even the range where it is a mix of both types.
by Chem_Mod
Sun Jul 14, 2019 11:53 am
Forum: Lewis Structures
Topic: Drawing lewis structures
Replies: 3
Views: 93

Re: Drawing lewis structures

Charged lewis structures follows the same process, however you want the overall formal charge to match. You would assign charges based on electronegativity strengths to see which ones will get the charge.
by Chem_Mod
Fri Jul 12, 2019 8:34 pm
Forum: Administrative Questions and Class Announcements
Topic: ASHLEY'S STEP UP WORKSHEETS
Replies: 15
Views: 512

Re: ASHLEY'S STEP UP WORKSHEETS

Here is the worksheet for my Step Up session this upcoming Monday. Feel free to take a look at it if you get the chance. If not, we will go over the questions step-by-step.
by Chem_Mod
Thu Jul 11, 2019 6:59 pm
Forum: Quantum Numbers and The H-Atom
Topic: What are the energy levels?
Replies: 1
Views: 106

Re: What are the energy levels?

Your question refers to the relationship between the quantum numbers.
See your class notes. For example, when n = 1 then l can only equal 0 (s-state).

Ask during the class break or at the end of class if this is not clear.

Review the section on quantum numbers.
by Chem_Mod
Thu Jul 11, 2019 1:07 pm
Forum: Ionic & Covalent Bonds
Topic: Ground State
Replies: 13
Views: 207

Re: Ground State

Yes, because the ground state configuration of Copper is [Ar]3d^(10)4s^(1), removing one electron to form the Copper ion gives you [Ar]3d^(10). Electrons are removed from the highest energy level, the 4s, before the 3d. Remember that the 4s orbital is higher in energy than the d orbitals after elect...
by Chem_Mod
Wed Jul 10, 2019 11:05 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Ground State vs. Excited State
Replies: 2
Views: 76

Re: Ground State vs. Excited State

Atoms in the excited state show configurations that do not follow the Aufbau principle. Orbitals are filled out of order or electrons are paired when empty orbitals of the same energy level are available.
by Chem_Mod
Wed Jul 10, 2019 11:03 pm
Forum: Lewis Structures
Topic: Double Bonds [ENDORSED]
Replies: 4
Views: 133

Re: Double Bonds [ENDORSED]

In addition, thinking about formal charges and which atoms can hold more (or less) than an octet will help you place the double bonds when not all of the possible positions are equivalent, which will be covered in lecture soon :)
by Chem_Mod
Wed Jul 10, 2019 11:00 pm
Forum: Ionic & Covalent Bonds
Topic: Homework 3.5
Replies: 7
Views: 160

Re: Homework 3.5

You are correct that 5s would be filled before 5d; however, the [Xe] is an abbreviation for all the orbitals that have already been filled up to Xenon's configuration, which includes the 5s orbital already.
by Chem_Mod
Wed Jul 10, 2019 10:58 pm
Forum: *Shrodinger Equation
Topic: General Question on Schrodinger Equation
Replies: 1
Views: 84

Re: General Question on Schrodinger Equation

The Schrodinger Equation is a mathematical equation that represents a wave. It can be solved, and a solution to the equation is an orbital. You will not need to know how to solve the equation for this class.
by Chem_Mod
Wed Jul 10, 2019 10:54 pm
Forum: Administrative Questions and Class Announcements
Topic: Michelle's Weekly Worksheets
Replies: 9
Views: 342

Re: Michelle's Weekly Worksheets

Week 3 worksheet for Thursday's workshop! Covers electron configurations, periodic trends, Lewis dot structures and resonance:
Chem 14A Summer 19 Wk 3 WS (1).docx
(6.75 KiB) Downloaded 16 times
by Chem_Mod
Wed Jul 10, 2019 7:43 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 6th edition chapter 3 problem 9
Replies: 2
Views: 71

Re: 6th edition chapter 3 problem 9

According to the Aufbau principle, the 4s sublevel is filled up before the 3d sublevel because the 4s sublevel is lower in energy so electrons in the 4s sublevel would be lost first. An ion with a +2 charge has loss two electrons, so its configuration would have two less electrons than it would have...
by Chem_Mod
Wed Jul 10, 2019 7:37 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuration for 1st row transition metals
Replies: 6
Views: 113

Re: Electron Configuration for 1st row transition metals

The special cases when completing ground state electron configurations are Cu and Cr. Its not all of the first row of transition metals.
by Chem_Mod
Wed Jul 10, 2019 10:56 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: ION WITH +1
Replies: 2
Views: 82

Re: ION WITH +1

Yes, an ion with a +1 charge means that it lost an electron so its configuration would have one less electron than it would it if it did not have a +1 charge.
by Chem_Mod
Tue Jul 09, 2019 9:22 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Atomic vs molecular electron transitions / spectroscopy
Replies: 1
Views: 83

Re: Atomic vs molecular electron transitions / spectroscopy

Atomic spectra are the transitions of electrons between electronic energy levels in isolated atoms. They are affected by the interactions of the transitioning electrons with the nuclei spins and with the other electrons in the atom. Molecular spectra involves transitions in molecules with two or mor...
by Chem_Mod
Tue Jul 09, 2019 9:16 pm
Forum: Administrative Questions and Class Announcements
Topic: homework this week?
Replies: 1
Views: 75

Re: homework this week?

Homework is still due this week in discussion sections as usual.
by Chem_Mod
Tue Jul 09, 2019 9:12 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Spectral lines
Replies: 1
Views: 52

Re: Spectral lines

Only specific wavelengths of light are absorbed in the atomic absorption spectrum. The correct answer should be B. It represents the wavelength of light absorbed by the gas sample.
by Chem_Mod
Tue Jul 09, 2019 9:04 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Rydberg's equation for midterm
Replies: 1
Views: 58

Re: Rydberg's equation for midterm

Yes, it is very likely that you will use Rydberg's equation for the midterm. For example, you may need it to solve for the frequency of light emitted by a hydrogen atom when an electron makes a transition from the fourth to the second principal quantum level.
by Chem_Mod
Tue Jul 09, 2019 9:01 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: 1 photon excites 1 electron?
Replies: 1
Views: 53

Re: 1 photon excites 1 electron?

Yes, you are correct. There is a one-to-one ratio between photons absorbed by a sample and the number of electrons that could possibly become excited to a higher energy level. The correct answer should be D. 1 million.
by Chem_Mod
Tue Jul 09, 2019 8:58 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Finding the initial energy level given frequency of emitted photon
Replies: 1
Views: 58

Re: Finding the initial energy level given frequency of emitted photon

Yes, that is the right place to begin. You can use the formula frequency = R (1/nf^2 - 1/ni^2), where ni is the initial energy level and nf is the final energy level. You can substitute all the values into the formula to solve for n. Your final energy level is n= 4 so nf = 4. You can plug in the Ryd...
by Chem_Mod
Tue Jul 09, 2019 8:45 pm
Forum: Administrative Questions and Class Announcements
Topic: Practice Midterm Answer Key
Replies: 1
Views: 106

Practice Midterm Answer Key

Here is the practice midterm answer key. Best of luck on your midterm!
by Chem_Mod
Tue Jul 09, 2019 2:55 pm
Forum: Administrative Questions and Class Announcements
Topic: Week 2 Butter Chicken Answers
Replies: 1
Views: 97

Week 2 Butter Chicken Answers

Here are answers for questions 1-8. The answer key for questions 9-16 will be posted soon.
by Chem_Mod
Tue Jul 09, 2019 2:23 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Quantitative Statement
Replies: 1
Views: 85

Re: Quantitative Statement

The correct answer should be D. (Indeterminacy in momentum) x (Indeterminacy in position) >= h/4pi. The more precisely the position is determined, the less precisely the momentum is known in one instant and vice versa. Stated qualitatively, there is a limit on the accuracy to which the momentum and ...
by Chem_Mod
Mon Jul 08, 2019 6:36 pm
Forum: Administrative Questions and Class Announcements
Topic: ASHLEY'S STEP UP WORKSHEETS
Replies: 15
Views: 512

Re: ASHLEY'S STEP UP WORKSHEETS

I have attached the answers to the worksheet, including some step-by-step calculations.
by Chem_Mod
Mon Jul 08, 2019 12:32 pm
Forum: Properties of Electrons
Topic: Rydberg Formula
Replies: 1
Views: 117

Re: Rydberg Formula

Rydberg Equation: 1/λ=R(1/n(1)^2−1/n(2)^2) You can change n(1) and n(2), which refer to different energy levels in the Hydrogen atom. For example, you can use n(1)= 1 and n(2)=2 to find the wavelength of light emitted when an electron drops from the n=2 to the n=1 energy level (or the wavelength of ...
by Chem_Mod
Mon Jul 08, 2019 12:25 pm
Forum: SI Units, Unit Conversions
Topic: Quantum Mechanics
Replies: 1
Views: 75

Re: Quantum Mechanics

Probability density is the probability that an electron can be found at a certain location around the nucleus. S orbitals are spherical and symmetric, so there is an equal chance of an electron being at any point in the s orbital. P orbitals are lobes with a node in the center, telling us that at th...
by Chem_Mod
Mon Jul 08, 2019 12:15 pm
Forum: Administrative Questions and Class Announcements
Topic: Practice Midterm
Replies: 1
Views: 119

Practice Midterm

Here is the practice midterm. Answers will be posted tomorrow.
by Chem_Mod
Mon Jul 08, 2019 12:15 pm
Forum: Properties of Electrons
Topic: Wave Properties of Electrons- Module Question
Replies: 1
Views: 77

Re: Wave Properties of Electrons- Module Question

The electrons have both wave-like and particle-like properties, and the photoelectric effect is a key example showing the particle-like property. The diffraction pattern observed during the experiment we went over in class is evidence that electrons have wave-like properties. As for the particle nat...
by Chem_Mod
Mon Jul 08, 2019 12:10 pm
Forum: Properties of Light
Topic: Light intensity [ENDORSED]
Replies: 2
Views: 102

Re: Light intensity [ENDORSED]

Yup, increasing intensity increases the number of photons being emitted per second, but the energy of each photon does not change
by Chem_Mod
Mon Jul 08, 2019 12:08 pm
Forum: Quantum Numbers and The H-Atom
Topic: Numbers
Replies: 2
Views: 95

Re: Numbers

The principle quantum number (n) represents the energy level The angular momentum quantum number (l) describes the shape of the orbital (s-,p-,d-) The magnetic quantum number (ml) labels the different orbitals (i.e. the orientations) of a subshell The spin magnetic quantum number (ms) tells the dire...
by Chem_Mod
Mon Jul 08, 2019 11:43 am
Forum: Quantum Numbers and The H-Atom
Topic: Predicting values based on quantum numbers
Replies: 1
Views: 69

Re: Predicting values based on quantum numbers

(a) For n = 7, you will have 7 values of l (0,1,2,3,4,5,6). (b) For a d subshell, you will have 5 values of ml because you have 5 orbitals. So, the value of ml would be (-2,-1,0,1,2). (c) For a p subshell, you will have 3 values of ml (-1,0,1). (d) n = 4 will have 4 subshells - s,p,d,f. So its l = 4...
by Chem_Mod
Mon Jul 08, 2019 10:57 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Stern and Gerlich Experiment
Replies: 1
Views: 62

Re: Stern and Gerlich Experiment

In this experiment, atoms were sent through a magnet field and deflected from a straight path depending on its electron spin. The collection plate on the other side of this magnetic field revealed discrete points of accumulation, rather than an expected continuous distribution. Through this experime...
by Chem_Mod
Mon Jul 08, 2019 10:48 am
Forum: Quantum Numbers and The H-Atom
Topic: 6th edition chapter 2 number 19
Replies: 1
Views: 91

Re: 6th edition chapter 2 number 19

You are correct in your answer for part(a), since you solve for "l" using (n-1). Given that n = 7, "l" can have any value from 0 to 6. For part(b), you solve for the magnetic quantum number (ml) by knowing the "l" value and can be solved using (-"l", 1-"l...
by Chem_Mod
Mon Jul 08, 2019 10:35 am
Forum: Quantum Numbers and The H-Atom
Topic: Homework 2.21
Replies: 1
Views: 58

Re: Homework 2.21

The principle quantum number is the same as "n", which tells us the energy level. The angular momentum quantum number is the same as "l", which tells us the shape of the orbital. Therefore, for 6p, the principle quantum number (n) is 6 and the angular momentum number (l) is 1. Th...
by Chem_Mod
Mon Jul 08, 2019 12:01 am
Forum: Administrative Questions and Class Announcements
Topic: Michelle's Weekly Worksheets
Replies: 9
Views: 342

Re: Michelle's Weekly Worksheets

Week 3 worksheet; review questions for the midterm taken from past worksheets
Chem 14A Summer 19 Wk 3 WS (MT review).docx
(7.01 KiB) Downloaded 25 times
by Chem_Mod
Sun Jul 07, 2019 11:39 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Homework 2.13
Replies: 1
Views: 54

Re: Homework 2.13

This problem would be best understood if you were to draw the graph. A Cartesian axis is an axis in 3D, having an X-, Y-, and Z-axis. The plane of the p-orbitals lie along the each of these axes .
by Chem_Mod
Sun Jul 07, 2019 11:33 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Subshells
Replies: 2
Views: 72

Re: Subshells

The shell (or "n") determines the energy level (i.e. n = 3)
The subshell (or "l") describes the shape of the orbital (i.e. l = 1 corresponds to p-orbital)
by Chem_Mod
Sun Jul 07, 2019 11:28 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Paired and Parallel Electrons
Replies: 1
Views: 57

Re: Paired and Parallel Electrons

Paired electrons have opposite spin and parallel electrons have the same spin. Recall the difference between the Pauli Exclusion Principle and Hund's Rule.
by Chem_Mod
Sun Jul 07, 2019 11:24 pm
Forum: Properties of Light
Topic: Homework 2.1
Replies: 1
Views: 57

Re: Homework 2.1

The value "l" represents a subshell, or the shape of orbital. It's value can be calculated by knowing the principle quantum number (n), and using n-1. "l" can range from 0 to 3. l = 0 corresponds to an s-orbital l = 1 corresponds to a p-orbital l = 2 corresponds to a d-orbital l ...
by Chem_Mod
Sun Jul 07, 2019 6:33 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: How do we know that an electron can't be between an energy level?
Replies: 3
Views: 96

Re: How do we know that an electron can't be between an energy level?

This is the basis of quantum mechanics, where the values are only discrete values, thus the "quantum" part. The energy of the photon must match the same energy to raise that electron to the next energy level, or else if it is lower or higher the photon will just pass through thus not being...
by Chem_Mod
Sun Jul 07, 2019 6:19 pm
Forum: Trends in The Periodic Table
Topic: Element Names
Replies: 2
Views: 97

Re: Element Names

The periodic table on the Chem 14A website is the same periodic table that will be provided to you on the test, and it includes both the name of the element along with its abbreviation. No memorization is required.
by Chem_Mod
Sun Jul 07, 2019 6:15 pm
Forum: Administrative Questions and Class Announcements
Topic: ASHLEY'S STEP UP WORKSHEETS
Replies: 15
Views: 512

Re: ASHLEY'S STEP UP WORKSHEETS

Here are the answers for the first worksheet! I had a question on number 3 on this worksheet. So, I got up to getting 4.74 x10^39 s.^-1 mol. ^-1, but I don't know what to do from there. I attempted using stoichiometry to convert my units, but I don't know what to use to do that. Can someone help???...
by Chem_Mod
Sun Jul 07, 2019 5:19 pm
Forum: Administrative Questions and Class Announcements
Topic: ASHLEY'S STEP UP WORKSHEETS
Replies: 15
Views: 512

Re: ASHLEY'S STEP UP WORKSHEETS

Yes, you are right that it should be 3.08 x 10^15. My apologies on the typo in the answer key!
by Chem_Mod
Sun Jul 07, 2019 1:44 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Nodes
Replies: 1
Views: 59

Re: Nodes

No. However it is important to have a good understanding of the what the shapes are telling you, which will then give reasoning to why there are certain nodes- places where no electron will be found- where they are. Remember that the pictures of the orbitals, as Dr. Lavelle said, that they are the m...
by Chem_Mod
Sun Jul 07, 2019 1:38 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: quantum numbers
Replies: 1
Views: 54

Re: quantum numbers

m(l) describes orientation because take for example the p block, where the shapes look like dumbells. However, that one dumbbell shape can have 3 different orientation, where the dumbbell aligns on the x, y, or z axis. Which is why m(l) has 3 numbers to describe the three different orientations, -1,...
by Chem_Mod
Sun Jul 07, 2019 10:50 am
Forum: Photoelectric Effect
Topic: Work function
Replies: 1
Views: 91

Re: Work function

You do not need to memorize any work functions for metals. The important part is understanding how to use the energy of photons and kinetic energies, which will be given indirectly, to find work functions.
by Chem_Mod
Sun Jul 07, 2019 10:49 am
Forum: Empirical & Molecular Formulas
Topic: Molar Mass vs. Atomic Weight
Replies: 7
Views: 208

Re: Molar Mass vs. Atomic Weight

Atomic mass is the mass of an atom. A single atom has a set number of protons and neutrons, so the mass is unequivocal (won't change) and is the sum of the number of protons and neutrons in the atom. Electrons contribute so little mass that they aren't counted. Atomic weight is a weighted average of...
by Chem_Mod
Sun Jul 07, 2019 10:48 am
Forum: Photoelectric Effect
Topic: Photo electric effect
Replies: 7
Views: 158

Re: Photo electric effect

The vacuum "vacuums" the air out it, which basically means there are no air molecules that are in the experiment, so all electrons that are ejected will go to the detector instead of interacting with air molecules.
by Chem_Mod
Sun Jul 07, 2019 10:47 am
Forum: Einstein Equation
Topic: 1.25 6TH Edition
Replies: 1
Views: 119

Re: 1.25 6TH Edition

Can you provide the context, such the main part of the question as well as the end goal. Thanks!
by Chem_Mod
Sun Jul 07, 2019 10:45 am
Forum: Einstein Equation
Topic: 1.13 sixth edition
Replies: 1
Views: 79

Re: 1.13 sixth edition

If you can provide the context and question of this problem that would be great.
by Chem_Mod
Fri Jul 05, 2019 3:01 pm
Forum: Administrative Questions and Class Announcements
Topic: ASHLEY'S STEP UP WORKSHEETS
Replies: 15
Views: 512

Re: ASHLEY'S STEP UP WORKSHEETS

Hello Everyone! I hope everyone had a great Fourth of July, and are now soon preparing for your midterm next week! Attached is the worksheet that I will be going over in my session on Monday. It includes problems that would be similar to what you may see on your midterm. Happy studies!
by Chem_Mod
Fri Jul 05, 2019 10:13 am
Forum: Balancing Chemical Reactions
Topic: balancing reaction law
Replies: 2
Views: 116

Re: balancing reaction law

You cannot add new reactants or products to a chemical equation. You can only change the ratio of what substances are there, using stoichiometric coefficients to balance the number of atoms.
by Chem_Mod
Fri Jul 05, 2019 10:06 am
Forum: Student Social/Study Group
Topic: July 5th hw
Replies: 1
Views: 75

Re: July 5th hw

The plan is to collect homework at the end of lecture.

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