Search found 45 matches

by Mario Reyes 1C
Fri Jun 08, 2018 6:33 pm
Forum: Dipole Moments
Topic: Why can't SO2 form Hydrogen bonds?
Replies: 3
Views: 462

Why can't SO2 form Hydrogen bonds?

On the homework problem 6.1 d) hydrogen bonding was not an answer. Why wouldn't SO2 be able to form hydrogen bonds, even though it has an oxygen with an available lone pair?
by Mario Reyes 1C
Fri Jun 08, 2018 6:15 pm
Forum: Dipole Moments
Topic: Are London dispersion forces present in every molecule?
Replies: 2
Views: 150

Are London dispersion forces present in every molecule?

Is it safe to say that London dispersion forces are present in every molecule? Are these forces within the molecule, or between neighboring molecules?
by Mario Reyes 1C
Mon Jun 04, 2018 9:11 pm
Forum: Hybridization
Topic: sp^3d or dsp^3
Replies: 6
Views: 262

sp^3d or dsp^3

Does it matter which way you write a hybridization with 5 regions of electron density? Is either way of writing it correct?
by Mario Reyes 1C
Sat Jun 02, 2018 9:48 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Significance of Coordination Number?
Replies: 7
Views: 265

Significance of Coordination Number?

Professor Lavelle stressed that the number of bonds equals the coordination number, but what makes the coordination number significant?
by Mario Reyes 1C
Sat Jun 02, 2018 9:37 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Chelate? [ENDORSED]
Replies: 2
Views: 97

Chelate? [ENDORSED]

I am a little confused on what a chelate is. Can someone explain?
by Mario Reyes 1C
Mon May 28, 2018 2:07 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: I3- Molecular Shape
Replies: 2
Views: 469

I3- Molecular Shape

Why is I3- linear and not bent? Would the 3 lone pairs on the central atom not cause the molecule to have a bent shape?
by Mario Reyes 1C
Sun May 27, 2018 6:22 pm
Forum: Sigma & Pi Bonds
Topic: Logic behind Sigma and Pi bonds?
Replies: 2
Views: 190

Logic behind Sigma and Pi bonds?

I understand that a sigma bond correlates to a single bond, and a double bond contains one sigma and one pi bond, but why is this?
by Mario Reyes 1C
Fri May 25, 2018 12:56 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Why do lone pairs occupy the most space? [ENDORSED]
Replies: 3
Views: 247

Why do lone pairs occupy the most space? [ENDORSED]

Lone pairs have the greatest repulsion strength because they occupy the most volume, but how do they occupy more volume than a bonding pair?
by Mario Reyes 1C
Mon May 21, 2018 5:56 pm
Forum: Lewis Structures
Topic: Lewis Structure tips?
Replies: 2
Views: 136

Lewis Structure tips?

When we finish completing a lewis structure and find that the formal charges of all atoms are not 0 in a neutral molecule (even though all the charges add up to 0), should we always try to make something a double/triple bond and try to make all the formal charges zero. It seems like a very tedious p...
by Mario Reyes 1C
Sun May 20, 2018 9:42 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Why don't we find the formal charge of Hydrogen?
Replies: 3
Views: 182

Re: Why don't we find the formal charge of Hydrogen?

Chem_Mod wrote:H only has 1 bond and always you have formal charge of 0 for this case.


What about when making chemical formulas for compounds. Is formal charge different from expected charges?
by Mario Reyes 1C
Sun May 20, 2018 9:31 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Why don't we find the formal charge of Hydrogen?
Replies: 3
Views: 182

Why don't we find the formal charge of Hydrogen?

This may have a simple answer, but why don't we find the formal charge of hydrogen in molecules?
by Mario Reyes 1C
Sun May 20, 2018 5:51 pm
Forum: Ionic & Covalent Bonds
Topic: 3.25 c)
Replies: 4
Views: 168

Re: 3.25 c)

Hydrogen can either have a charge of positive or negative 1 but since Aluminum already assumes the positive charge, you use the Hydrogen charge of 1- to construct your formula :) Thank you! Do you know why it can be +1 or -1? I feel it is because it can add 1 electron to fill its outermost shell, b...
by Mario Reyes 1C
Sun May 20, 2018 4:43 pm
Forum: Lewis Structures
Topic: 3.33 c). Ionization energy question.
Replies: 4
Views: 124

Re: 3.33 c). Ionization energy question.

I thought you put the molecule with the lowest electronegativity in the center, are ionization energy and electronegativity the same thing? My TA also said to put the least electronegative in the center, but professor Lavelle said in lecture to put the lowest ionization energy in the center. I'm no...
by Mario Reyes 1C
Sun May 20, 2018 4:38 pm
Forum: Lewis Structures
Topic: 3.33 c). Ionization energy question.
Replies: 4
Views: 124

Re: 3.33 c). Ionization energy question.

Using periodic trends this is true, but from what I remember those are only general trends and there are exceptions. Nitrogen has a half full shell which makes it more stable than Oxygen. This results in a slightly higher ionization energy for Nitrogen, because the Nitrogen wants to keep it's half f...
by Mario Reyes 1C
Sun May 20, 2018 4:06 pm
Forum: Lewis Structures
Topic: 3.33 and ionization energy
Replies: 3
Views: 147

Re: 3.33 and ionization energy

We actually choose the atom with the lowest ionization energy for the central atom. Even with that, part c) is still confusing since O has a lower ionization energy than N does. Anybody understand why?
by Mario Reyes 1C
Sun May 20, 2018 4:02 pm
Forum: Lewis Structures
Topic: 3.33 c). Ionization energy question.
Replies: 4
Views: 124

3.33 c). Ionization energy question.

When writing lewis structures we put the atom with the lowest ionization energy in the center. For 3.33, part c asks for ONF. The answer shows that N is in the center, but doesn't O have a lower ionization energy? Can someone explain this.
by Mario Reyes 1C
Sun May 20, 2018 2:55 pm
Forum: Ionic & Covalent Bonds
Topic: 3.25 c)
Replies: 4
Views: 168

3.25 c)

On the basis of the expected charges on the monatomic ions, give the chemical formula of each of the following compounds: (c) aluminum hydride.

Al has a 3+ charge, and I think Hydride is referring to Hydrogen. I am confused on what charge Hydrogen would have.
by Mario Reyes 1C
Sun May 20, 2018 2:07 pm
Forum: Dipole Moments
Topic: Difference between Dipole-Dipole and Dipole-Induced dipole?
Replies: 2
Views: 99

Difference between Dipole-Dipole and Dipole-Induced dipole?

In my notes I have both these examples with H-F H-F for dipole-dipole and H-Cl N-N(triple bond) for dipole-induced dipole. What is the difference between these two?
by Mario Reyes 1C
Sun May 20, 2018 2:03 pm
Forum: Dipole Moments
Topic: London Dispersion, Induced dipole- Induced dipole, Van Der Waals
Replies: 5
Views: 198

London Dispersion, Induced dipole- Induced dipole, Van Der Waals

In class Professor Lavelle said these are all similar, so is there really no difference to these forces besides the name?
by Mario Reyes 1C
Fri May 18, 2018 3:43 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Does being more polarizable= Being stronger?
Replies: 2
Views: 259

Does being more polarizable= Being stronger?

In regards to the example of CH4 and CCl4, CCl4 has a higher boiling point. This is because it has more electrons and is more polarizable, so does this mean being more polarizable means being stronger? Also, F2 and Cl2 being gases at room temp, while Br2 is a liquid and I2 is a solid. Does this foll...
by Mario Reyes 1C
Sun May 13, 2018 1:36 pm
Forum: Resonance Structures
Topic: Resonance Structures
Replies: 5
Views: 2285

Re: Resonance Structures

Also, if you do draw all resonance structures be sure to include the double headed arrow between each of them. Maybe it's not that big of a deal but he explicitly mentioned that in class.
by Mario Reyes 1C
Sun May 13, 2018 1:31 pm
Forum: Lewis Structures
Topic: Lewis Structures
Replies: 4
Views: 172

Re: Lewis Structures

I'm pretty sure it depends on which has a lower formal charge. This may also have to deal with vsepr which we haven't got to yet.
by Mario Reyes 1C
Sun May 13, 2018 1:26 pm
Forum: Lewis Structures
Topic: Ammonium Sulfate Example in Notes
Replies: 2
Views: 82

Re: Ammonium Sulfate Example in Notes

Be sure to skip the transition metals when trying to count the number of valence electrons from left to right.
by Mario Reyes 1C
Tue May 08, 2018 1:13 pm
Forum: Trends in The Periodic Table
Topic: Does Sulfur or Phosphorus have a larger ionization energy?
Replies: 3
Views: 1229

Does Sulfur or Phosphorus have a larger ionization energy?

Using the trends it would seem like Sulfur would have a larger ionization energy, but just like oxygen and nitrogen, the phosphorus is half filled. Does this mean Phosphorus has a larger ionization energy?
by Mario Reyes 1C
Mon May 07, 2018 3:16 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Drawing Lewis Structures
Replies: 5
Views: 236

Drawing Lewis Structures

When drawing a lewis structure, why do we choose the atom with the lowest ionization energy as the central atom?
by Mario Reyes 1C
Sun May 06, 2018 11:26 pm
Forum: Trends in The Periodic Table
Topic: 2.67 part c) and d) [ENDORSED]
Replies: 5
Views: 225

Re: 2.67 part c) and d) [ENDORSED]

I'm confused by the reasoning. I thought electron affinity was dealing with adding electrons, not taking them away.
by Mario Reyes 1C
Sun May 06, 2018 9:23 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Why isn't Vanadium an exception?
Replies: 2
Views: 123

Why isn't Vanadium an exception?

I understand why Chromium and Copper are exceptions using the symmetry argument. However, why isn't Vanadium an exception as well? The configuration for Vanadium is [Ar]3d^3 4s^2. Why don't the 2 electrons from 4s go to 3d to fill the d orbital?
by Mario Reyes 1C
Sun May 06, 2018 9:07 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: f block elements
Replies: 2
Views: 98

f block elements

When writing electron configurations where you need to include the f block, why is the principal quantum number 2 behind the row. For example, for Tungsten the electron configuration is [Xe]4f^14 5d^4 6s^2. I understand the d block is 1 less, but why is the f block 2 less?
by Mario Reyes 1C
Wed May 02, 2018 1:29 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: What does ground state mean? [ENDORSED]
Replies: 4
Views: 236

What does ground state mean? [ENDORSED]

From what I know ground state means the electron configuration follows the Pauli Exclusion Principle and the Hunds Rule. Is there anything else to this?
by Mario Reyes 1C
Wed May 02, 2018 12:43 pm
Forum: Quantum Numbers and The H-Atom
Topic: Principle quantum number and orbital angular momentum quantum number
Replies: 2
Views: 117

Re: Principle quantum number and orbital angular momentum quantum number

l CAN equal 0, 1, 2 ,3 ,and 4. However, this doesn't mean that l will equal all of those values. In this case they tell us l=2 which indicates that electrons are in the p orbital.
by Mario Reyes 1C
Sun Apr 29, 2018 1:19 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Short hand? [ENDORSED]
Replies: 1
Views: 96

Short hand? [ENDORSED]

When using short hand, when can you only use preceding inner gases? Why can't you use any other element before it?
by Mario Reyes 1C
Sun Apr 29, 2018 1:17 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: What does electron spin actually mean? [ENDORSED]
Replies: 9
Views: 379

What does electron spin actually mean? [ENDORSED]

When saying two electrons spin in opposite directions, what is that really saying?
by Mario Reyes 1C
Fri Apr 27, 2018 3:33 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Why does the 4s orbital come before the 3d?
Replies: 7
Views: 262

Why does the 4s orbital come before the 3d?

If I heard correctly in class, the 4s orbital comes before 3d only for elements with 20 electrons or less. Can somebody explain why?
by Mario Reyes 1C
Sun Apr 22, 2018 10:58 pm
Forum: DeBroglie Equation
Topic: Post-Assessment #34 [ENDORSED]
Replies: 5
Views: 185

Re: Post-Assessment #34 [ENDORSED]

Maya Khoury wrote:I attached a picture below of me trying to find the speed for this problem but for some reason i always end up with a ridiculously large number. Can someone tell me what I'm doing wrong? I'm sure it's a stupid mistake lol

thank you !


The denominator should be 10^-39, not 10^-49
by Mario Reyes 1C
Sun Apr 22, 2018 10:47 pm
Forum: DeBroglie Equation
Topic: How do you calculate speed using the De Broglie equation? [ENDORSED]
Replies: 6
Views: 241

Re: How do you calculate speed using the De Broglie equation? [ENDORSED]

So rearranged, the equation for velocity would be plancks constant / (wavelength)(mass) correct? I used this equation for #34 solving for speed and did not get the correct answer, which was the reason I was unsure if speed and velocity were the same.
by Mario Reyes 1C
Sun Apr 22, 2018 10:24 pm
Forum: DeBroglie Equation
Topic: How do you calculate speed using the De Broglie equation? [ENDORSED]
Replies: 6
Views: 241

How do you calculate speed using the De Broglie equation? [ENDORSED]

I do not understand how to calculate speed using the De Broglie equation? Is it the same as calculating the velocity? If so, how do you calculate the velocity?
by Mario Reyes 1C
Mon Apr 16, 2018 8:46 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: #42 In Post-Module Assessment [ENDORSED]
Replies: 5
Views: 174

Re: #42 In Post-Module Assessment [ENDORSED]

Since it is Efinal- Einitial, shouldn't it be E4-Ex?

Also, I am confused on these steps. How did you get -6.06x10^-20?

Ex = (-hr)/x^2 = -6.06 X 10^-20

x^2 = 35.9

x = n = 6
by Mario Reyes 1C
Mon Apr 16, 2018 6:43 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: #42 In Post-Module Assessment [ENDORSED]
Replies: 5
Views: 174

#42 In Post-Module Assessment [ENDORSED]

The question asks 'An excited hydrogen atom emits light with a frequency of 1.14 x 10^14 Hz to reach the energy level n = 4. In what principle quantum level did the electron begin?' A. n = 5 B. n = 6 C. n = 4 D. n = 7 I am not sure how to approach this problem. Would we have to plug in every quantum...
by Mario Reyes 1C
Sun Apr 15, 2018 4:20 pm
Forum: Photoelectric Effect
Topic: Intensity VS Energy Models? [ENDORSED]
Replies: 4
Views: 158

Re: Intensity VS Energy Models? [ENDORSED]

To add on to this, does light intensity matter for the photoelectric effect? It does matter in terms of how many electrons are emitted. If the energy of the photon is above the threshold, then increasing the intensity would cause more electrons to be emitted since intensity can be thought of as num...
by Mario Reyes 1C
Sun Apr 15, 2018 12:36 pm
Forum: Properties of Light
Topic: Threshold Energy [ENDORSED]
Replies: 3
Views: 115

Re: Threshold Energy [ENDORSED]

If you are given the energy of the photon and the excess energy, you can solve for the threshold energy by adding them together.
by Mario Reyes 1C
Sun Apr 15, 2018 12:32 pm
Forum: Photoelectric Effect
Topic: Intensity VS Energy Models? [ENDORSED]
Replies: 4
Views: 158

Re: Intensity VS Energy Models? [ENDORSED]

If we used the wave model increasing the intensity of the light should eject electrons from the metal surface, because increasing intensity of the light means increasing the energy since that increases the amplitude of the wave. However, this was not the case and electrons were not ejected even when...
by Mario Reyes 1C
Thu Apr 12, 2018 5:09 pm
Forum: Photoelectric Effect
Topic: Why do shorter wavelengths have more energy than longer wavelengths?
Replies: 4
Views: 225

Why do shorter wavelengths have more energy than longer wavelengths?

I know short wavelengths (high frequency) have more energy than longer wavelengths, but I really don't know why. I partially understand why using the E=hc/lambda equation, but I do not understand the logic behind it.
by Mario Reyes 1C
Sun Apr 08, 2018 10:59 pm
Forum: SI Units, Unit Conversions
Topic: Moles mols mol? [ENDORSED]
Replies: 21
Views: 1274

Re: Moles mols mol? [ENDORSED]

I typically see the textbook use "mols" but I'm sure either way works. As long as you don't leave it as "M" which is molarity, you're fine.
by Mario Reyes 1C
Sun Apr 08, 2018 10:56 pm
Forum: Balancing Chemical Reactions
Topic: Naming Molecules [ENDORSED]
Replies: 1
Views: 96

Naming Molecules [ENDORSED]

I think I remember in class professor Lavelle saying that he didn't expect us to know the names of complicated molecules, but we still got some homework problems asking us to name them. Will we need to know the names of molecules and know their molecular formula for this class, or will they be provi...
by Mario Reyes 1C
Sun Apr 08, 2018 10:51 pm
Forum: Limiting Reactant Calculations
Topic: Limiting Reagent and finding amount produced
Replies: 2
Views: 184

Re: Limiting Reagent and finding amount produced

I like the car analogy that he used in class. You have to use the limiting reactant to find out how much product can be made, because that is the reactant that limits how much is produced. In other words, that is the maximum amount you can possibly get. In his analogy, he said that tires were the li...

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