Gen chem questions

 What properties would a different mass number (A) affect?
A different mass number will affect the mass of that particular atom, and the number of neutrons in that atom.  Different mass numbers correspond to different isotopes -- for example, Carbon-12, 13, and 14 have different mass numbers, but they all have 6 protons and 6 electrons.  They have 6, 7, and 8 neutrons, respectively.

 Where did angular momentum equation (both of them) come from?

1. L=mvR , Avg momentum of electron = nh / 2Π

The first one comes from physics (rotational motion).  This is NOT something you are required to know for the MCAT.  It says that the angular momentum is equal to the mass of the object, m, times its velocity, v, times the radius of the orbit, R.  The second one is a quantum-mechanical devised formula.  I'm not sure of its derivation, but it's a definition from the quantum model.

2. Also, where did quantized energy of electron come from? E = -R_n­­­­  / n_­­­²  This comes originally from Bohr's model of the atom (remember passage one from Gen Chem I lesson), and corresponds to the energy for a given principal number.

3.  Negative sign of energy equation, E = -R_n­­­­  / n_­­­²    What is equation showing? (Is it PE?)

This is indeed potential energy.  It's negative because the force this energy comes from is an attractive force.  In general, this means that increasing principal quantum number means higher (less negative) energy.

4.  Why isn’t equation 8 the normal equation of final – initial for E =hc/  = -R_n [1/ni² - 1/nf²] ?

It still is.  They've factored out the Rydberg constant in the equation.

5.  Explain Atomic emission spectra versus absorption spectra.  What is exactly happening and what does spectra look like?

When electrons jump up in energy (to a higher n value), they need to absorb energy to do so.  That's the absorption spectra.  When they drop in energy, they give off this energy -- that's the emission spectra.  Conveniently, this often corresponds to light energy in the visible spectrum, which means that we can see what wavelengths of light are absorbed or emitted if we pass all wavelengths of light through a sample of that atom.  It can be used as like a "fingerprinting" for an element -- every element has a different absorption and emission spectra.  A good visual is provided here:  http://www.cartage.org.lb/en/themes/Sciences/Astronomy/Modenastronomy/Interactionoflight/AtomicAbsorption/spectra.gif

6. What is the difference between shell, subshell, orbital? Could you provide a visual?

Think of this like the assigned seating analogy.  A different shell is like a different section in a stadium, a different subshell is a different row, a different orbital is a different seat.  Within a shell, there may be many subshells; within a subshell, there may be many orbitals.

7.  -do you need to memorize the formulas for the quantum numbers?
   1. -need to see visual for each?

Visual is provided in question 6 - assigned seating.  And yes, you do want to know the various quantum numbers available, given a specific principle quantum number.

1. -Is Table 1.2, m_l row incorrect with two zeros? What’s the order?

There are two available spins (+/- 1/2), so there are two different electrons that can be in the same ml = 0 orbital.

8.  Would violating any of the other rules, such as Hund’s Rules also violate the Pauli Exclusion principle? I originally thought the violation would be Hund’s Rule? (But such answer choice is not available)?

Depending on the circumstance, you could violate more than one rule if you're doing something that's not scientifically possible.  Do know, however, that the Pauli exclusion principle is not violatable in the natural world.

9. What is considered “inner transition” vs. the “transition elements” and could you explain the rationale behind the different rules for counting valence electrons?

"Inner transition" are the lanthanide and actinide series (f block).  "Transition" are the d block (Sc-Zn and the elemens below them).  Valence electrons work as follows:
s block:  1 or 2, depending on which group
p block:  2+how far over in the p block (i.e., O = 2+4 = 6)
d block:  2+how far over in the d block (i.e., V = 2+3 = 5)
f block:  2 +how far over in the f block (similar to above).

1. Doesn’t the number of valence electrons for sulfur depend on the resonance structure chosen for sulfate?
2. Different resonance structures mean different arrangements of electrons, and thus (possibly) different formal charges.  The valence electrons when an element is unbound is a constant (for sulfur, it's 6).  And while different resonance structures CAN mean different numbers of valence electrons in the BOUNDED state, all the resonance structures of sulfate have the same number of valence electrons around sulfur.