Search found 37 matches

by Sameen Mahmood 3D
Sat Dec 08, 2018 2:19 pm
Forum: Lewis Acids & Bases
Topic: Can someone please explain the heme group/hemoglobin stuff?
Replies: 2
Views: 69

Re: Can someone please explain the heme group/hemoglobin stuff?

A transition metal is often found bound to a cage-like molecule, for example the porphyrin ligand. (4 nitrogens in a plane, creating a tetra-dentate square planar) Iron is bound to this porphyrin ligand, and therefore creates a HEME complex. A heme complex and a protein create myoglobin, which is t...
by Sameen Mahmood 3D
Fri Dec 07, 2018 7:41 pm
Forum: Lewis Acids & Bases
Topic: Can someone please explain the heme group/hemoglobin stuff?
Replies: 2
Views: 69

Can someone please explain the heme group/hemoglobin stuff?

Can someone explain it clearly and what exactly we need to know about it for the final?? Thank you!
by Sameen Mahmood 3D
Tue Dec 04, 2018 2:32 pm
Forum: Bronsted Acids & Bases
Topic: Determining Acidity
Replies: 3
Views: 90

Re: Determining Acidity

Whichever molecule is the easiest to break (easiest to remove H+) is the most acidic.
by Sameen Mahmood 3D
Tue Dec 04, 2018 2:29 pm
Forum: Conjugate Acids & Bases
Topic: Inductive Effect
Replies: 5
Views: 137

Re: Inductive Effect

I don't think we need to know inductive effects for the final. Was it discussed during lecture?
by Sameen Mahmood 3D
Tue Dec 04, 2018 2:28 pm
Forum: Sigma & Pi Bonds
Topic: Strength of Sigma and Pi Bonds
Replies: 5
Views: 316

Re: Strength of Sigma and Pi Bonds

Sigma bonds overlap more closely across the internuclear axis. The concentration of electrons brings the nuclei closer together (harder to detach).
by Sameen Mahmood 3D
Fri Nov 30, 2018 9:58 pm
Forum: Bronsted Acids & Bases
Topic: What are conjugate acids and bases??
Replies: 2
Views: 79

What are conjugate acids and bases??

Can someone define conjugate acids and bases?
by Sameen Mahmood 3D
Fri Nov 30, 2018 9:56 pm
Forum: Dipole Moments
Topic: Induced Dipole - Induced Dipole
Replies: 3
Views: 121

Re: Induced Dipole - Induced Dipole

Additionally, for induced dipole-induced dipole, the induced dipoles actually form because of the random arrangement of electrons in a nonpolar molecule. Just by chance, it's possible that one region of the molecule has a partial charge, causing nearby molecules to have their electron clouds distort...
by Sameen Mahmood 3D
Fri Nov 30, 2018 9:53 pm
Forum: Administrative Questions and Class Announcements
Topic: DOWNLOAD SESSION WORKSHEETS HERE - Sundays 4-6pm (Karen) [ENDORSED]
Replies: 135
Views: 28847

Re: DOWNLOAD SESSION WORKSHEETS HERE - Sundays 4-6pm (Karen) [ENDORSED]

Are these worksheets based on the homework and test problems directly or are they independent?
by Sameen Mahmood 3D
Fri Nov 30, 2018 9:52 pm
Forum: Lewis Acids & Bases
Topic: Differentiating Between Lewis and Bronsted
Replies: 2
Views: 63

Re: Differentiating Between Lewis and Bronsted

I second the previous comment. Also for a quick pneumonic, you can just think of it as Lewis - lone pair and Bronsted - (B)roton. I know it's kind of weird but it works for me lol.
by Sameen Mahmood 3D
Fri Nov 30, 2018 9:51 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Covalent Character
Replies: 2
Views: 237

Re: Covalent Character

Covalent character has to do with polarizability in ionic compounds. MgBr2 has more covalent character than NaBr because Mg has a charge of 2+, meaning that it has high polarizing power, so it can more easily distort the electron cloud of Br.
by Sameen Mahmood 3D
Tue Nov 20, 2018 3:08 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: lone pairs
Replies: 4
Views: 83

Re: lone pairs

They affect neighboring atoms slightly by pushing on them but they don't create significant changes in bond angle (think CH4 vs. CH3Cl).
by Sameen Mahmood 3D
Tue Nov 20, 2018 3:08 pm
Forum: Hybridization
Topic: Bond Angles
Replies: 4
Views: 78

Re: Bond Angles

You could also have them memorized by considering 360 degree planes and types of repulsion that are going on in the molecule.
by Sameen Mahmood 3D
Tue Nov 20, 2018 3:06 pm
Forum: Hybridization
Topic: d Orbital
Replies: 6
Views: 79

Re: d Orbital

You don't need to know the exact shape but remember identifying generalities
by Sameen Mahmood 3D
Wed Nov 14, 2018 3:06 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Determining VSEPR bond angles
Replies: 5
Views: 111

Re: Determining VSEPR bond angles

Will we be tested on bond angles at all? If so, is there a set amount of angles that we should memorize? I definitely think we will be tested on them considering they're discussed in lectures, discussions, and homework. Plus it helps you to visualize the spatial arrangement of the molecule in terms...
by Sameen Mahmood 3D
Wed Nov 14, 2018 3:03 pm
Forum: Bond Lengths & Energies
Topic: Bond Length and Resonance
Replies: 5
Views: 171

Re: Bond Length and Resonance

Generally, the longer a bond, the weaker a bond. Because triple bonds consist of very high electron density between two atoms, the charges are centralized between the two nuclei which brings them closer together, creating a stronger, shorter bond. And with resonance yes the bonds are the same as lon...
by Sameen Mahmood 3D
Wed Nov 14, 2018 3:01 pm
Forum: Octet Exceptions
Topic: Radicals
Replies: 16
Views: 535

Re: Radicals

The atom with an incomplete lone electron pair is what makes the molecule a radical molecule. Typically it'll be like nitrogen or something. Because they're reactive they don't last very long and they can be very damaging.
by Sameen Mahmood 3D
Wed Nov 14, 2018 2:58 pm
Forum: Electronegativity
Topic: Electronegativity in Molecules with N,O,F
Replies: 4
Views: 149

Re: Electronegativity in Molecules with N,O,F

As long as the hydrogen itself is attached to a N, O, or F, it can be attracted to N, O, or F of another molecule.
by Sameen Mahmood 3D
Wed Nov 14, 2018 2:56 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Electron density
Replies: 6
Views: 129

Re: Electron density

Yes, the electron density around the central atom is the one we use to determine molecular shape. Though regions of electron density refer to lone pairs and bonding regions, so I think they can refer to atoms other than the central atom.
by Sameen Mahmood 3D
Wed Nov 14, 2018 2:54 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bent vs Angular
Replies: 3
Views: 87

Re: Bent vs Angular

I disagree with the previous post, they are synonyms but I've only seen bent in the lectures/discussions/homework so I'd just use bent for consistency. It's simpler to remember bent as opposed to "angular" anyway, it seems more accurate to the shape we're talking about.
by Sameen Mahmood 3D
Wed Nov 14, 2018 2:53 pm
Forum: Resonance Structures
Topic: Formal Charge
Replies: 13
Views: 456

Re: Formal Charge

It does matter what formal charges the atoms have because you are always looking for the most ideal/stable structure. In general, more electronegative atoms should have negative formal charges as opposed to less electronegative ones. Granted, you would want them all to be zero ideally, but if the ov...
by Sameen Mahmood 3D
Wed Nov 14, 2018 2:51 pm
Forum: Administrative Questions and Class Announcements
Topic: Octet Rule
Replies: 6
Views: 196

Re: Octet Rule

Well keep in mind that there are elements that break the octet rule, not just elements in period 3 or greater that can have expanded valence (because they can use the d orbitals) but also elements such as Boron or Aluminum which generally only form three bonds. It wouldn't be good to have a boron wi...
by Sameen Mahmood 3D
Wed Nov 14, 2018 2:49 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 3
Views: 67

Re: Bond Angles

Considering they're always being brought up not just in lectures but also discussions and homework, I definitely think we'll be asked for bond angles for all structures.
by Sameen Mahmood 3D
Wed Oct 31, 2018 1:13 am
Forum: Lewis Structures
Topic: Valence Electrons
Replies: 7
Views: 119

Re: Valence Electrons

Elements in period 3 or later that have a d subshell
by Sameen Mahmood 3D
Wed Oct 31, 2018 1:12 am
Forum: Lewis Structures
Topic: Stable Lewis Structures
Replies: 4
Views: 83

Re: Stable Lewis Structures

The structure that gives the most number of individual atoms a formal charge of 0 is the most stable. Ideally overall FC would be 0 too.
by Sameen Mahmood 3D
Wed Oct 31, 2018 1:12 am
Forum: Lewis Structures
Topic: Lewis Structure of BrF3 [ENDORSED]
Replies: 3
Views: 239

Re: Lewis Structure of BrF3 [ENDORSED]

Actually bromine needs an octet BUT it can occupy more than an octet because it's an element in period 3 or later (it can occupy more electrons because of the presence of the d subshell). It's just a rule you have to memorize.
by Sameen Mahmood 3D
Wed Oct 24, 2018 9:32 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Bohr Freq Cond relation to Spectroscopy
Replies: 1
Views: 76

Re: Bohr Freq Cond relation to Spectroscopy

E=hv can be applied to describe the energy released by a given photon from an atom. The energy of a released photon correlates to its frequency and thereby its wavelength, so the wavelength emitted can be deduced using E=hv, and this generates the lines you see in emission spectra. I don't recall go...
by Sameen Mahmood 3D
Wed Oct 24, 2018 9:26 am
Forum: Einstein Equation
Topic: Equations for Light Only
Replies: 3
Views: 438

Re: Equations for Light Only

All of the equations are given on the test and you can use all of them for everything based on the conditions given. The only restriction is De Broglie because it only applies to things with rest mass.
by Sameen Mahmood 3D
Wed Oct 24, 2018 9:25 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: exceptions: chromium & copper
Replies: 2
Views: 68

Re: exceptions: chromium & copper

No, the rule for atoms after Z=20 having 4s higher than 3d still applies.
by Sameen Mahmood 3D
Wed Oct 24, 2018 9:21 am
Forum: Properties of Light
Topic: Visible Light Spectrum... ?
Replies: 6
Views: 128

Re: Visible Light Spectrum... ?

Basically know the following: 400-700nm = visible light, <400 nm = UV, >700 nm = IR
by Sameen Mahmood 3D
Wed Oct 24, 2018 9:20 am
Forum: DeBroglie Equation
Topic: De Broglie wavelengths
Replies: 3
Views: 127

Re: De Broglie wavelengths

De Broglie wavelengths are used for large particles as well as anything that has rest mass. You'll know when to use it based on the parameters given; for instance, if you are given mass, velocity, momentum, or wavelength, you can predict that you'll have to use De Broglie because the other equation ...
by Sameen Mahmood 3D
Wed Oct 24, 2018 9:18 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Question About Valence Electrons
Replies: 1
Views: 57

Question About Valence Electrons

Are valence electrons the electrons in the outermost subshell or shell? For instance, if looking at the valence electrons for phosphorous (Z=15), are we only considering the number of electrons in the 3p orbitals or all of the n=3 orbitals (3s and 3p)? Prof. Lavelle said in class while he was drawin...
by Sameen Mahmood 3D
Tue Oct 16, 2018 5:20 pm
Forum: Properties of Light
Topic: Threshold Energy
Replies: 4
Views: 45

Re: Threshold Energy

The electron is still completely dissociated from the atom, it just has no kinetic energy and therefore it doesn't have movement on its own. If it does move, its because the detector has a positive charge, not because the electron has its own kinetic energy since all of the energy given by the photo...
by Sameen Mahmood 3D
Tue Oct 16, 2018 5:18 pm
Forum: Properties of Light
Topic: property of light
Replies: 2
Views: 45

Re: property of light

You can utilize the information given in the question to derive an answer without considering photons in terms of their energy as a particle/wave. Because you are given wavelength, use the equation E=hv to find the energy and multiply it by the number of photons.
by Sameen Mahmood 3D
Tue Oct 16, 2018 5:14 pm
Forum: Properties of Electrons
Topic: electromagnetic radiation
Replies: 3
Views: 79

Re: electromagnetic radiation

The photoelectric effect treats the incoming wavelength of light as a beam of photons, with each photon essentially being able to "knock out" an electron from a given atom as long as it has enough energy. We also discussed that the intensity of light is described as the number of photons p...
by Sameen Mahmood 3D
Fri Oct 12, 2018 2:09 pm
Forum: Einstein Equation
Topic: Delta E values
Replies: 2
Views: 69

Re: Delta E values

For the equation E=hv, you're trying to calculate the energy of a photon. The energy of an emitted photon can never be negative, that just doesn't make sense. When we discuss a negative delta E we're talking about a loss of energy. That equation doesn't deal with energy change; the equation E=(-hR)/...
by Sameen Mahmood 3D
Fri Oct 12, 2018 2:06 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Wavelike properties
Replies: 7
Views: 84

Re: Wavelike properties

All matter has wavelike properties, but anything smaller than 10^-18m is neglible. Usually anything that doesn't have an extremely small mass or extremely fast velocity (like an electron) will generate numbers like 10^-30m for their wavelength, so the aren't actually waves bc their wavelength is eve...
by Sameen Mahmood 3D
Fri Oct 12, 2018 2:01 pm
Forum: Limiting Reactant Calculations
Topic: How to determine the limiting reactant???? [ENDORSED]
Replies: 8
Views: 1116

Re: How to determine the limiting reactant???? [ENDORSED]

Another method would be to find the moles of each reactant and compare the ratio of the calculated moles to the reaction's moles. For ex, if you have 1 mol C and 2 mol H, but the reactants' side is something like C+H, you know the 1:1 ratio isn't met. H is present in excess (you have more than what ...

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