Search found 30 matches

by Emma Leshan 1B
Tue Jun 12, 2018 6:49 pm
Forum: Lewis Acids & Bases
Topic: HW 12.17 [ENDORSED]
Replies: 4
Views: 336

Re: HW 12.17 [ENDORSED]

I don't understand why SO3 is acidic. I don't see why it would accept protons. Doesn't it already have -2 charge?
by Emma Leshan 1B
Tue Jun 12, 2018 10:39 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: HW 17.33
Replies: 6
Views: 291

Re: HW 17.33

Ligands are more likely to be polydentate if there are many atoms between the ones with lone pairs. This allows the molecule to bend, interacting with the metal in more than one place. Also, I think one reason CO3 2- can't be tridentate is due to its double bond, which would make it harder for the m...
by Emma Leshan 1B
Sun Jun 03, 2018 12:49 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: formal charge and VSEPR
Replies: 8
Views: 263

Re: formal charge and VSEPR

VSEPR refers to the notation and also the way of finding the molecular shape from the Lewis structure.
by Emma Leshan 1B
Sun Jun 03, 2018 12:46 pm
Forum: Hybridization
Topic: σ bonds
Replies: 9
Views: 276

Re: σ bonds

Remember how the p-orbitals are oriented: one along the x-axis, one along the y-axis, and one along the z-axis. Because of this orientation, only one of the bonds can overlap the orbitals and be a sigma bond. The other orbitals are side-by-side and therefore form pi bonds. <img src="https://d2g...
by Emma Leshan 1B
Sun Jun 03, 2018 12:40 pm
Forum: Hybridization
Topic: Hybridization and it's relation to valence electrons
Replies: 3
Views: 101

Re: Hybridization and it's relation to valence electrons

So if there's a double bond, and 2 single bonds on carbon, the hybridization would be sp2? How does that work in respect to valence electrons?
by Emma Leshan 1B
Sun May 27, 2018 6:59 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polarity
Replies: 2
Views: 81

Re: Polarity

You have to look at the electronegativity of each element involved. Technically, every covalent bond has polarity unless it is between 2 of the same elements (O2 for example). However, some bonds are more polar (example: C-H bonds are less polar than O-H bonds) due to the differences in electronegat...
by Emma Leshan 1B
Sun May 27, 2018 6:56 pm
Forum: Lewis Structures
Topic: 2 lone pairs
Replies: 5
Views: 198

Re: 2 lone pairs

Remember that a Lewis Structure is just a 2D model of a 3D shape. So for example, in water, with a tetrahedral shape, every region of electron density is next to every other, so there is no "top" or bottom. With Lewis structures, it doesn't matter where you draw the lone pairs because it d...
by Emma Leshan 1B
Sun May 27, 2018 10:11 am
Forum: Bond Lengths & Energies
Topic: 3.85 part b
Replies: 3
Views: 214

Re: 3.85 part b

Both Lewis structures have one double bonded O and the other(s) are single bonded. Because of resonance, the double bonds are shared throughout the molecule. This makes the bond lengths approximately equal in the molecules even though technically SO2 should be a little shorter due to the double bond...
by Emma Leshan 1B
Sun May 20, 2018 1:50 pm
Forum: Dipole Moments
Topic: Dipole moment as a vector [ENDORSED]
Replies: 2
Views: 105

Re: Dipole moment as a vector [ENDORSED]

The partial negative results from the electrons being pulled toward the more electronegative atom, which is why the arrow points toward the partial negative: that is the way the electrons are being pulled.
by Emma Leshan 1B
Sun May 20, 2018 1:47 pm
Forum: Administrative Questions and Class Announcements
Topic: Absent Friday
Replies: 4
Views: 334

Re: Absent Friday

We discussed the strength of the interactions Alejandro listed as well as what effect interaction strength has on properties of a compound.
by Emma Leshan 1B
Wed May 16, 2018 3:14 pm
Forum: Formal Charge and Oxidation Numbers
Topic: In Class Example, Re: radicals, NO
Replies: 2
Views: 114

Re: In Class Example, Re: radicals, NO

Remember that O always has an octet because of its high electronegativity, and that should help.
by Emma Leshan 1B
Wed May 16, 2018 3:12 pm
Forum: Formal Charge and Oxidation Numbers
Topic: formal charge
Replies: 11
Views: 449

Re: formal charge

Formal charge = number of lone pair electrons - 1/2 * number of bonding electrons
by Emma Leshan 1B
Sat May 05, 2018 10:03 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Homework 2.55
Replies: 2
Views: 106

Re: Homework 2.55

Group 15 includes N, P, As, Sb, Bi. Each has a valence electron configuration of (n-1)d10 ns2 np3, the d group is not included because the electrons in the d subshell are in the shell n-1, so they aren't valence electrons. For example, arsenic has a configuration of [Ar] 3d10 4s2 4p3. Because the d ...
by Emma Leshan 1B
Sat May 05, 2018 9:57 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]

Also, since chlorine and sodium have fewer electrons, there is less shielding, making the effective nuclear charge larger and making it harder to remove electrons.
by Emma Leshan 1B
Sat May 05, 2018 9:23 pm
Forum: Trends in The Periodic Table
Topic: 2.67 part C (electron affinity)
Replies: 3
Views: 93

Re: 2.67 part C (electron affinity)

I was wondering this too, so I looked it up. Apparently, a half-filled p subshell is more stable than one with only 2 electrons, so this is why carbon has a higher electron affinity than nitrogen.
by Emma Leshan 1B
Sun Apr 29, 2018 2:13 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Short hand? [ENDORSED]
Replies: 1
Views: 96

Re: Short hand? [ENDORSED]

Inert gases have a full outer energy shell, so using them is basically saying that the last energy shell is completely full, and then you add the rest of the configuration for whichever atom you are specifying. For example, if I was talking about carbon, I would say [He] 2s^2 2p^2 to say that n=1 is...
by Emma Leshan 1B
Sun Apr 29, 2018 2:03 pm
Forum: Quantum Numbers and The H-Atom
Topic: Fourth Quantum Number
Replies: 5
Views: 181

Re: Fourth Quantum Number

I don't think you necessarily need to calculate whether the spin is up or down, you just need to know that if there are 2 electrons occupying the same orbital, one will spin up and one down.
by Emma Leshan 1B
Sun Apr 29, 2018 1:59 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: h-bar [ENDORSED]
Replies: 7
Views: 273

Re: h-bar [ENDORSED]

The Uncertainty Equation stated in the textbook has 1/2 * h-bar, and since h-bar is h/2pi, we use h/4pi.
by Emma Leshan 1B
Mon Apr 23, 2018 7:59 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Rydberg Equation [ENDORSED]
Replies: 3
Views: 186

Re: Rydberg Equation [ENDORSED]

If we find it faster and easier to use the Rydberg equation on a test or quiz, are we allowed to use it as long as we understand the concepts?
by Emma Leshan 1B
Sun Apr 22, 2018 12:06 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: The Negative Sign in En = -hR/n^2
Replies: 5
Views: 159

Re: The Negative Sign in En = -hR/n^2

So as a follow up, when using the Rydberg equation, the negative is there for the same reason? Is it because the Rydberg equation is derived from this equation? When calculating frequency from the Rydberg equation, we could just ignore the negative, correct?
by Emma Leshan 1B
Sat Apr 21, 2018 9:11 pm
Forum: Photoelectric Effect
Topic: Significance of intensity [ENDORSED]
Replies: 7
Views: 215

Re: Significance of intensity [ENDORSED]

Continuing off that note, when light acts as a wave, or for any wave, the intensity relates to the amplitude/height of the wave.
by Emma Leshan 1B
Sat Apr 21, 2018 9:09 pm
Forum: Properties of Light
Topic: units for frequency and wavelength [ENDORSED]
Replies: 9
Views: 262

Re: units for frequency and wavelength [ENDORSED]

I believe it's preferred for very small wavelengths such as ones in the visible region to be written in nanometers, but you won't get points off for writing it in meters.
by Emma Leshan 1B
Sat Apr 21, 2018 9:05 pm
Forum: Properties of Light
Topic: HW #1.57 [ENDORSED]
Replies: 1
Views: 95

Re: HW #1.57 [ENDORSED]

The first wavelength (656.3) is the longest, meaning it has the lowest energy. This must mean it must result from the smallest energy level transition. Since the Balmer series is for visible light, it involves n=2. In this case, the fist stated wavelength is for the transition n1=2 to n2=3, the smal...
by Emma Leshan 1B
Sun Apr 15, 2018 2:38 pm
Forum: Properties of Light
Topic: Value of speed of light [ENDORSED]
Replies: 4
Views: 178

Re: Value of speed of light [ENDORSED]

Use whichever constant is given on the test just to be safe.
by Emma Leshan 1B
Sun Apr 15, 2018 2:38 pm
Forum: Properties of Light
Topic: Data to memorize for this chapter [ENDORSED]
Replies: 2
Views: 119

Re: Data to memorize for this chapter [ENDORSED]

Also, Dr Lavelle said all the equations would be on the test, but you should know how to use them. I'm sure he doesn't expect us to memorize the EM spectrum, as he gives all constants on the tests. Hope this helps!
by Emma Leshan 1B
Fri Apr 13, 2018 5:05 pm
Forum: Photoelectric Effect
Topic: Post module quiz #25
Replies: 6
Views: 156

Post module quiz #25

25. Photoelectric experiments gave rise to a new equation relating the energy of light to its frequency. Select the right equation. A. λv = c B. Ek = mv2/2 C. mv2/2 = hv - φ D. E = hv E. None of the above I thought the answer would be c, but it said this was wrong. Can someone please explain?
by Emma Leshan 1B
Sat Apr 07, 2018 7:54 pm
Forum: Molarity, Solutions, Dilutions
Topic: Review Worksheet [ENDORSED]
Replies: 3
Views: 155

Re: Review Worksheet [ENDORSED]

I also find it very helpful to use unit conversions aka dimensional analysis to solve problems like this. For example, you know 0.12*750mL will give you the volume in mL. Now you want to find the mass in grams, so you need the units to be g/mL in order for mL to cancel, and you'll be left with grams...
by Emma Leshan 1B
Sat Apr 07, 2018 7:44 pm
Forum: Balancing Chemical Reactions
Topic: Common Compounds to know
Replies: 3
Views: 207

Re: Common Compounds to know

Dr Lavelle said after class that we wouldn't be expected to know this for the first test.
by Emma Leshan 1B
Sat Apr 07, 2018 7:40 pm
Forum: Balancing Chemical Reactions
Topic: Balancing equations with fractions [ENDORSED]
Replies: 13
Views: 493

Re: Balancing equations with fractions [ENDORSED]

Definitely multiply the whole thing by 2. Dr Lavelle said in class that stoichiometric coefficients should be whole numbers.

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