CHEMISTRY COMMUNITY

Andrew Lam 3B

Thank you Dr. Lavelle for making your lectures informative and engaging. It has been easy to keep up with the material presented and I am looking forward to 14B next quarter.

Andrew Lam 3B

pi bonds form between p orbitals -- there are 3 of them per atom

Andrew Lam 3B

Strong acids/base reactions go so far towards dissociation we assume they completely dissociate, so no equilibrium constant needs to be solved for. (There are basically no reactants left)

Andrew Lam 3B

Pi bonds bond above and below the molecule and lock the molecule in place, preventing rotation unlike sigma bonds who bond at one point in the center

Andrew Lam 3B

Single, Double, Triple bonds all counts as one region of electron density.

Andrew Lam 3B

I think it's just more of a stylistic thing and personal preference.

Andrew Lam 3B

AX4E is Seesaw (dsp3), AX4E2 is Square Planar (d2sp3)

Andrew Lam 3B

Dimagnetic elements have no unpaired electrons, while paramagnetic elements have at least 1.

Andrew Lam 3B

sp: 1/2
sp2: 1/3
sp3: 1/4
dsp3: 1/5
d2sp3: 1/6

It's the ratio of the orbitals.

Andrew Lam 3B

Lone pairs take up more space than bonding pairs, so instead of 109.5 for tetrahedral you get 104.5 and bent.

Andrew Lam 3B

Lone pairs take up more space than bonding pairs, depressing the bond angle.

Andrew Lam 3B

It would probably be safe to know the most common ones just in case they come up on a test.

Andrew Lam 3B

The water molecules are more attracted to one another (dipoles) than to the oil molecules. The oil molecules are said to be hydrophobic and do not mix with water for this reason.

Andrew Lam 3B

Lone pairs on neighboring atoms would repel one another because they are all negative (only electrons form lone pairs). This weakens the bond in question.

Andrew Lam 3B

The oxygen molecule on water has 2 lone pairs that cause the bond angle to be slightly depressed to around 109.5; this is called a bent configuration.

Andrew Lam 3B

Generally the most stable configuration is one where the formal charge is minimized on all the atoms involved. Usually you don't have to draw them but it can be helpful if a test question were to ask of the two lewis structures which one is favored.

Andrew Lam 3B

It shows up on a lot of old midterms but I'm guessing they had already gotten to hybridization by that point. I don't think it would show up on tomorrow's midterm (that would be a really unfair question)

Andrew Lam 3B

Do you guys know how many points total you can get taken off of the midterm if you miss sig figs and units, but get all of the math/concepts right? Looking at previous midterms, you usually lose 1 or 2 points per problem for sig figs or units if you mess either up. So for a question say Q4A, Q4B, a...

Andrew Lam 3B

For Problem 2.49 "Predict the number of valence electrons present in each of the following atoms (include the outermost d-electrons: (a) N; (b) Ag; (c) Nb; (d) W." What trend are we expected to see in order to identify the number of valence electrons? The atomic number? Is there also some...

Andrew Lam 3B

In 2.29 part c), I don't understand why the maximum number of electrons is 8 if n=2. Can someone please explain? At energy level 2, there are two possible subshells: s and p. (Remember that 2d and 2f do not exist). The s subshell can hold 2 electrons, while the 3 p orbitals combined hold 6 electron...

Andrew Lam 3B

For Exercise 2.29 (Chapter 2 The Quantum Mechanics in Action: Atoms) How many electrons can have the following quantum numbers in an atom: a) n = 2, l = 1 b) n = 4, l = 2, ml = -2 c) n = 2 d) n = 3, l = 2, ml = +1 Does anyone know how to solve this problem? Thank you in advance The question varies i...

Andrew Lam 3B

The wave properties do exist for relatively large objects, but those wavelengths are so small we do not have equipment that can detect waves in the 10^-35 spectrum.

Andrew Lam 3B

ml is used to describe the individual orbital within a subshell.

For l = 0 (s orbital), then the only ml possible is 0 (there is only one s orbital).
For l = 1 (p orbital), you can have ml = -1 (px), 0 (py), or 1 (pz), and so forth for other orbitals.

Andrew Lam 3B

The p-orbital experiences less pull from the nucleus because some of the repulsion from s-orbital electrons are also affecting it. Thus, we need something called effective nuclear charge to describe the binding strength of electrons. They are the same energy level (in the case of 2s and 2p) but are ...

Andrew Lam 3B

Diatomics exist to share electrons covalently and achieve a lower energy state.

HOFBrINCl is a metonym to remember the diatomics:
H- Hydrogen
O- Oxygen
F- Fluorine
Br- Bromine
I- Iodine
N- Nitrogen
Cl- Chlorine

Andrew Lam 3B

Atoms with low electron affinity (i.e. alkali metals) lose electrons far more easily to have a full valence shell whereas it is far easier for a halogen (say Fluorine) to pick up an electron and fill its valence shell. Thus, we say halogens have a high electron affinity.

Andrew Lam 3B

In essence, you can never have light that strikes in 1.2 photons, 5.64 photons, etc. The particle nature of light only travels in whole number of "packets".

Andrew Lam 3B

Silver generally is found in the +1 oxidation state.

Other ones of note are Iron being +2 or +3, copper being +1, etc.

Andrew Lam 3B

M_initialV_initial = M_finalV_finak

M_initial = 0.2109 M
V_initial = 0.02 L (Only 20.0 mL is transferred)
V_final = 0.250 L

Solve for M_final, which should be 1.69 x 10^-2 M

Andrew Lam 3B

If it looks like or is close to a fraction, multiply by its inverse to clear a fraction
(e.g. x.3333 multiply by 3, x.25 multiply by 4, x.2 multiply by 5, x.5 multiply by 2, x.75 multiply by 4/3)

If its close to a whole number, just round up (x.9545 just round to the next number)

CHEMISTRY COMMUNITY

Search found 30 matches

Re: Saying Thank You to Dr. Lavelle

Re: Number of Sigma and Pi Bonds

Re: Equilibrium Constants

Re: Pi bonds

Re: Double Bonds as Regions of Electron Density

Re: Just Kind of Confused

Re: Seesaw or Square Planar

Re: test #3

Re: s-character

Re: Bond Angles for H2O

Re: lone pair influence on shape

Re: Bond Angles

Re: Polar and Nonpolar Molecules

Re: Lone Pairs on Neighboring Atoms

Re: VSEPR Model for Water

Re: Formal Charge and Lewis Structures

Re: Midterm1

Re: Chem Midterm

Re: Exercise 2.29

Re: Exercise 2.29

Re: Exercise 2.29

Re: Wave properties of large particles

Re: ml Quantum Number

Re: Shielding [ENDORSED]

Re: diatomic elements

Re: electron affinity [ENDORSED]

Re: Quanta & Photons

Re: Question E16 - Transition Metal Charge

Re: Study Module Post-assessment Question

Re: Mutiplying by a number