Search found 40 matches

by madijohnson_4A
Fri Dec 06, 2019 10:45 am
Forum: Resonance Structures
Topic: midterm #7a [ENDORSED]
Replies: 1
Views: 46

Re: midterm #7a [ENDORSED]

PO4 3- has resonance, so its true structure is a blend of all 4 possible resonance structures. Because of the delocalized electrons, all of the bond lengths will be the same, and be somewhere in between the single bond and double bond lengths.
by madijohnson_4A
Fri Dec 06, 2019 10:41 am
Forum: Naming
Topic: Easy way to memorize
Replies: 1
Views: 31

Re: Easy way to memorize

I would start by creating flashcards based on the table for naming coordination compounds he has on his class website. Once you have the common ligand names down, you just write them in alphabetical order with the correct prefixes (representing the number of each ligand), and write the metal at the ...
by madijohnson_4A
Fri Dec 06, 2019 10:33 am
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: bond strength
Replies: 2
Views: 45

Re: bond strength

As you go down a row, the bond becomes longer and therefore weaker than the bonds with elements above it. The longer bonds are due to larger nuclei, more core electrons shielding the valence electrons, and decreasing electronegativity. The longer the bond, the easier it is to break and dissociate in...
by madijohnson_4A
Fri Dec 06, 2019 10:29 am
Forum: Sigma & Pi Bonds
Topic: Sigma & Pi Bonds Role in structure and shape
Replies: 2
Views: 41

Re: Sigma & Pi Bonds Role in structure and shape

Sigma bonds allow molecules to rotate whereas pi bonds fixate molecules in that position. Molecules with sigma bonds, therefore, are more flexible in structures.
by madijohnson_4A
Fri Dec 06, 2019 10:27 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordination #
Replies: 6
Views: 59

Re: Coordination #

In question 9C.9 from the homework, why are the coordination numbers from part C and D 6?
by madijohnson_4A
Sun Nov 24, 2019 9:01 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polarity
Replies: 3
Views: 39

Re: Polarity

I feel like there will probably be polarity questions on more complicated molecules. Also, in LS 7A you need to be able to determine polarity of larger organic molecules, so even if we don't use it now, we'll need it in other classes.
by madijohnson_4A
Sun Nov 24, 2019 8:58 pm
Forum: Lewis Acids & Bases
Topic: Lewis vs. Bronsted Acids and Bases
Replies: 2
Views: 28

Re: Lewis vs. Bronsted Acids and Bases

A Lewis acid is an electron pair acceptor, and a Lewis base is an electron pair donor.
A Bronsted acid gives up an H+ (proton donor), and a Bronsted base receives an H+ (proton acceptor).
by madijohnson_4A
Sun Nov 24, 2019 8:53 pm
Forum: Naming
Topic: Oxidation
Replies: 14
Views: 129

Re: Oxidation

The oxidation number represents the number of electrons gained or lost by an element. For example, the oxidation number of oxygen in a compound is usually -2 because oxygen typically gains two electrons in a chemical reaction. However, the oxidation number of a neutral element is always zero (exampl...
by madijohnson_4A
Sun Nov 24, 2019 8:51 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Test 2
Replies: 2
Views: 38

Re: Test 2

I would email your TA and ask if they are holding office hours next week and if you could pick it up then.
by madijohnson_4A
Sun Nov 24, 2019 8:48 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: T-Shape
Replies: 5
Views: 52

Re: T-Shape

In the Lewis structure, it looks like the electrons pairs are right next to each other, but in the VSEPR model they are much further apart with the 3D shape. For example with water, it looks like the lone pairs are right next to each other, but they are actually spaced out in the tetrahedral shape f...
by madijohnson_4A
Fri Nov 15, 2019 11:45 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 6
Views: 37

Re: Bond Angles

As a side note, if there are multiple bond angles within the shape (like 120 and 90 degree angles within a trigonal bipyramidal molecule), we don't have to indicate which angles go where, we can just say the angles will be less than 120 and less than 90 for a shape like seesaw with 5 regions of elec...
by madijohnson_4A
Fri Nov 15, 2019 11:41 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge
Replies: 9
Views: 105

Re: Formal Charge

I'm not sure how people do formal charge so quickly in their heads, I always need to write it out personally, but the ones I've memorized are:
double bonded oxygen with 2 lone pairs has a formal charge of 0
single bonded oxygen with 3 long pairs has a formal charge of -1
I hope this helps a little!
by madijohnson_4A
Fri Nov 15, 2019 11:35 pm
Forum: Dipole Moments
Topic: Xenon
Replies: 4
Views: 48

Re: Xenon

He was also saying that the molecular structures involving Xenon are very rare because it is a noble gas and usually won't react.
by madijohnson_4A
Fri Nov 15, 2019 11:33 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Symmetry and Polarity
Replies: 13
Views: 98

Re: Symmetry and Polarity

The Lewis structure won't show you the polarity, but it is helpful in determining the VSEPR model shape of the molecule which will then help determine polarity. If the VSEPR shape allows for dipole moments to cancel and the overall dipole moment to be zero, then the molecule will be nonpolar.
by madijohnson_4A
Fri Nov 15, 2019 11:29 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Determining if a molecule is polar or non polar
Replies: 9
Views: 63

Re: Determining if a molecule is polar or non polar

I don't think we need to memorize exact electronegativities, but knowing the trends in electronegativity would probably be helpful to determine what bonds would be polar vs nonpolar. In general, the electronegativity increases as you move diagonally up and to the right of the periodic table.
by madijohnson_4A
Sun Nov 03, 2019 10:23 am
Forum: Lewis Structures
Topic: Lowest Energy
Replies: 2
Views: 22

Re: Lowest Energy

The best way to determine the lowest energy structure is to look at the formal charge: the closer to zero the formal charge is, the more energetically favorable the structure is.
by madijohnson_4A
Sun Nov 03, 2019 10:21 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Nodal Planes
Replies: 1
Views: 28

Re: Nodal Planes

The nodal planes are the area where you will not find electrons- they basically just give a more detailed description of electrons within the orbital.
by madijohnson_4A
Sun Nov 03, 2019 10:19 am
Forum: Resonance Structures
Topic: Resonance Stability
Replies: 3
Views: 23

Re: Resonance Stability

Molecules with resonance are more stable because resonance spreads multiple bond character over a molecule which lowers the energy. The lower the energy, the more stable the molecule.
by madijohnson_4A
Sun Nov 03, 2019 10:14 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Quantum Numbers and subshells
Replies: 2
Views: 31

Re: Quantum Numbers and subshells

I don't think we have to know anything other than the s, p, d and f orbitals so I wouldn't worry too much about it!
by madijohnson_4A
Sun Nov 03, 2019 10:12 am
Forum: Bond Lengths & Energies
Topic: Bond Strength
Replies: 6
Views: 33

Re: Bond Strength

The shorter bonds are double and triple bonds which share more electrons than longer single bonds. The more electrons are shared, the shorter the bonds are because there is more pull from the nuclei on the electrons. The increase number of shared electrons are what make shorter bonds stronger.
by madijohnson_4A
Sun Oct 27, 2019 11:00 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Question about the Principles on Tests
Replies: 5
Views: 62

Re: Question about the Principles on Tests

It's probably a good idea to be familiar with the concepts by name just to be safe!
by madijohnson_4A
Sun Oct 27, 2019 10:58 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Wave Functions
Replies: 2
Views: 30

Re: Wave Functions

I believe the wave function describes the height of the wave at position (x,y,z) in a field. Not sure why the wave function squared represents the probability, but I hope that helps!
by madijohnson_4A
Sun Oct 27, 2019 10:55 pm
Forum: Trends in The Periodic Table
Topic: Cations vs Parent atoms
Replies: 4
Views: 36

Re: Cations vs Parent atoms

Cations have less electrons and less electron-electron repulsion compared to the parent atom, so the electrons are pulled in more by the nucleus.
by madijohnson_4A
Sun Oct 27, 2019 10:53 pm
Forum: Student Social/Study Group
Topic: Need Notes
Replies: 10
Views: 185

Re: Need Notes

Claire Grover 3G wrote:Does anyone have the notes from lecture last Friday (10/11)? I couldn't see well from where I was sitting and want to clarify a few things. Thanks so much!


If you still need the notes from Friday I have them! Just let me know how to send them to you.
by madijohnson_4A
Sun Oct 27, 2019 10:47 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: electron configuration
Replies: 1
Views: 26

Re: electron configuration

I'm pretty sure you're right and we won't have to go past the 3d orbitals because most biological molecules stay within those first three energy levels, and the 4s orbital.
by madijohnson_4A
Wed Oct 16, 2019 10:39 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Incorrect Atom Model
Replies: 3
Views: 39

Re: Incorrect Atom Model

When you work out the velocity for the electron when it is confined within the 1.7x10^-15 m of the nucleus, the velocity is 3.4x10^10 which is greater than the speed of light (3.00x10^8). The unrealistic velocity value is telling us that the electron cannot be confined within the nucleus.
by madijohnson_4A
Wed Oct 16, 2019 10:35 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: the fourth number?
Replies: 4
Views: 45

Re: the fourth number?

The fourth number is really just there to demonstrate that the electrons are not identical: they are spinning in opposite directions.That is why the options for ms are +1/2 and -1/2.
by madijohnson_4A
Wed Oct 16, 2019 10:33 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Untrue PSI From Lecture
Replies: 2
Views: 44

Re: Untrue PSI From Lecture

In the first energy level, n=1, the only possible orbital that can be found is an s orbital with l=0 because there are only 2 electrons in available to fill the first energy level.
by madijohnson_4A
Wed Oct 16, 2019 10:29 pm
Forum: General Science Questions
Topic: Chemistry Community Registration
Replies: 2
Views: 56

Re: Chemistry Community Registration

I would try using the "contact us" button at the bottom of the screen and tell them about your problem because it seems very odd and like quite the nuisance. I'm sorry you're dealing with that.
by madijohnson_4A
Wed Oct 16, 2019 10:18 pm
Forum: Quantum Numbers and The H-Atom
Topic: Quantum Numbers question, ml
Replies: 2
Views: 53

Re: Quantum Numbers question, ml

The possible values for ml are l, l-1, and -l.

When l=1, those values of ml are 1 (l); 1-1=0 (l-1); and -1 (-l).
When l=0, the only possible value of ml is 0 because 0-0=0 and -0 is also just 0.
by madijohnson_4A
Thu Oct 10, 2019 5:52 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Absorption Spectrum
Replies: 2
Views: 76

Re: Absorption Spectrum

In order for the electron to be excited to another energy level, the incoming photon must have the exact energy difference between the energy levels. Therefore, a photon with too much energy could not be absorbed.
by madijohnson_4A
Thu Oct 10, 2019 5:48 pm
Forum: Limiting Reactant Calculations
Topic: Fundamentals M.5
Replies: 3
Views: 93

Re: Fundamentals M.5

Since the stoichiometric relationship between the ClO2 and BrF3 is 6:2, there should be three times more ClO2 than BrF3. Since you know BrF3 is in excess, take the amount of ClO2 (12 mol) and divide it by 3 to get the number of moles of BrF3 that should be used up in the equation (4). Then, take the...
by madijohnson_4A
Thu Oct 10, 2019 5:43 pm
Forum: Properties of Light
Topic: Energy Levels
Replies: 8
Views: 120

Re: Energy Levels

UV radiation is the highest energy. Everything related to n=1 is in the UV region because it takes the most energy to go from n=1 to any other energy level due to the inverse squared relationship of n in the empirical equation for the H-atom: En= -(hR)/(n)^2.
by madijohnson_4A
Thu Oct 10, 2019 10:58 am
Forum: Administrative Questions and Class Announcements
Topic: Can't find my old posts
Replies: 1
Views: 40

Re: Can't find my old posts

If you go up to quick links in the top left corner of the page, there should be a section called "your posts" and that will show you all of the posts you've made. If your tenth post doesn't show up, I would make another post just in case.
by madijohnson_4A
Thu Oct 10, 2019 10:53 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Photon Absorption/Emission
Replies: 8
Views: 124

Re: Photon Absorption/Emission

Is there a sign difference between the energy emitted versus the energy absorbed even though they are the same value? Like is the energy emitted a negative value and the energy absorbed positive?
by madijohnson_4A
Wed Oct 02, 2019 11:04 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7951
Views: 1118592

Re: Post All Chemistry Jokes Here

I don't trust atoms... I heard they make up everything.
by madijohnson_4A
Wed Oct 02, 2019 10:57 pm
Forum: Empirical & Molecular Formulas
Topic: QUESTION F.21 HW
Replies: 3
Views: 41

Re: QUESTION F.21 HW

Was F.21 assigned in the homework?
by madijohnson_4A
Wed Oct 02, 2019 10:56 pm
Forum: Ideal Gases
Topic: Module Questions- Balancing Equations
Replies: 4
Views: 113

Re: Module Questions- Balancing Equations

The net number of moles is the overall moles produced in the reaction. The way you find it is to take the moles of product and subtract the moles of reactants.
by madijohnson_4A
Mon Sep 30, 2019 10:08 am
Forum: Significant Figures
Topic: All students read this sig fig post [ENDORSED]
Replies: 116
Views: 12190

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

Does Dr. Lavelle prefer rounding or truncating digits for the final answer?
by madijohnson_4A
Mon Sep 30, 2019 10:04 am
Forum: Administrative Questions and Class Announcements
Topic: Advice from a Medical Student - Part II [ENDORSED]
Replies: 150
Views: 4831

Re: Advice from a Medical Student - Part II [ENDORSED]

Thank you so much for your inspiring insight and story about your journey. It is really amazing to see someone who was in our shoes just a little while ago doing such amazing things. Do you have any advice for undergraduates potentially interested in medical school on when and how to study for the M...

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