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wXt_tUPtAe8-017|Every 10-electron species that's slightly excited-- that is, has a 3s1 electron-- will have this electronic configuration. |
wXt_tUPtAe8-018|Electronic configurations are not unique. |
wXt_tUPtAe8-019|If you have to put 10 electrons around an atom, you have to put them in a certain way. |
wXt_tUPtAe8-020|It's the number of protons that determine what the atom actually is, whether it's a sodium or fluorine. |
wXt_tUPtAe8-021|The number of electrons is completely independent. |
wXt_tUPtAe8-022|I could have too many electrons, I could have a negative ion, I can remove electrons and have the positive ion. |
wXt_tUPtAe8-023|So almost any element can have almost any electronic configuration. |
wXt_tUPtAe8-024|So you have to know, to determine the species, the number of protons in the nucleus. |
wXt_tUPtAe8-025|We don't know that here. |
k3ISd1oHxKA-000|If I have a particle that has wavelike properties and is trapped in a box, we understand that it has different energy states. |
k3ISd1oHxKA-001|And how do I make a transition between one energy state and the next energy state? |
k3ISd1oHxKA-002|Well, I absorb energy. |
k3ISd1oHxKA-006|Now, I haven't drawn A and B to scale. |
k3ISd1oHxKA-007|The question is, which transition is bigger, has the larger energy transition? |
k3ISd1oHxKA-008|Is A bigger than B? |
k3ISd1oHxKA-009|Are they about the same, or is A smaller than B? |
k3ISd1oHxKA-013|We're looking at identical particles trapped in two different boxes, one box twice the size of the other box. |
k3ISd1oHxKA-015|Well, you could calculate the energies based on this expression. |
k3ISd1oHxKA-016|But you could also just look at the energy levels of both boxes. |
k3ISd1oHxKA-017|Here's n equals 1, for instance, for the smaller box, and n equals 2 for the smaller box. |
k3ISd1oHxKA-018|n equals 1 for the larger box here, and n equals 2 for the larger box. |
k3ISd1oHxKA-019|And here's where you notice something interesting. |
k3ISd1oHxKA-020|If n equals 2 and you put that into the expression, you get a 2 here and a 2L here. |
k3ISd1oHxKA-022|So you get cancellation in the 2 case for both the larger box and n equal 1 case for the smaller box. |
k3ISd1oHxKA-023|Those energy levels turn out to be the same. |
k3ISd1oHxKA-026|So the correct answer here, A transition smaller than B transition. |
SKjxtaGYxjk-000|Let's look at the periodic table in a slightly different way. |
SKjxtaGYxjk-001|What I've done here is I've written out the periodic table and I've represented by dots the number of electrons in the outermost shell. |
SKjxtaGYxjk-006|And if you have the same number of valence electrons, you'll have the same properties. |
SKjxtaGYxjk-007|You'll react the same. |
SKjxtaGYxjk-008|You'll bond the same to other atoms. |
SKjxtaGYxjk-009|And that's why, in the periodic table, elements with similar properties line up because they have similar numbers of valence electrons. |
SKjxtaGYxjk-010|So our valence electrons go from one to eight along principal quantum level two and from one to eight along principal quantum level three. |
SKjxtaGYxjk-014|Neon and argon have a closed shell, stable octet of electrons. |
SKjxtaGYxjk-015|They're not as reactive as their counterparts in the corresponding rows. |
SKjxtaGYxjk-016|Same thing with helium, it's a closed shell of two electrons. |
SKjxtaGYxjk-017|That's the maximum number of electrons in principle quantum level one. |
SKjxtaGYxjk-018|And helium is also not very reactive. |
SKjxtaGYxjk-019|But what we're going to look at now is how these valence electrons affect the bonding and the reactions of the elements in the periodic table. |
SKjxtaGYxjk-020|In fact, reactions and bonding are the subject of pretty much the rest of chem one. |
WVLx-q-hZGk-000|Let's look at the titration of a strong acid with a strong base, our strong acid, HCl, and our strong base, NaOH. |
WVLx-q-hZGk-001|HCl, the strong acid, totally dissociates in water. |
WVLx-q-hZGk-002|In fact, that's the definition of strong acid-- totally dissociates in water. |
WVLx-q-hZGk-003|NaOH totally dissociates in water. |
WVLx-q-hZGk-004|That's a strong base. |
WVLx-q-hZGk-005|If I titrate an HCl solution with 0.1 molar NaOH, I get this titration curve. |
WVLx-q-hZGk-006|The question is, how does the titration curve change if I titrate with 0.2 molar NaOH? |
WVLx-q-hZGk-014|We're talking about titrating HCl, a strong acid, with two different strong base solutions. |
WVLx-q-hZGk-015|One, 0.1 molar, and then doing it again with 0.2 molar strong base. |
WVLx-q-hZGk-016|The question is, how does that second-- 0.2 molar-- pH curve look? |
WVLx-q-hZGk-017|Well, the initial HCl concentration is the same, so I'm titrating the same acid solution. |
WVLx-q-hZGk-018|So the starting point is the same. |
WVLx-q-hZGk-019|So A is out already. |
WVLx-q-hZGk-024|So the new pH curve will look like this, an equivalence point twice as early in half the volume. |
WVLx-q-hZGk-025|And that's selection C. The correct answer here is C. |
4nVIxjOAAGY-002|Now, that's what I do for steric number two. |
4nVIxjOAAGY-005|How about steric number three? |
4nVIxjOAAGY-006|When I've steric number three, I need to accommodate bond angles of 120 degrees. |
4nVIxjOAAGY-011|So hybridisation allows us to accommodate the geometry for various steric numbers. |
ZwsWjelzqDA-000|Particles, especially tiny ones, have a wavelike property that we can resolve. |
ZwsWjelzqDA-001|And we saw that with electrons going through a crystal diffracting. |
ZwsWjelzqDA-003|It actually gets a little spookier than that. |
ZwsWjelzqDA-006|It's a very, very, very spooky property of matter. |
ZwsWjelzqDA-007|And from here on in chemistry we're going to talk about those very spooky quantum properties of matter. |
ZwsWjelzqDA-008|Let's start by looking at a classic experiment or a classic calculation, a particle in a box. |
ZwsWjelzqDA-009|You can imagine taking a particle that has a wavelike property and trapping it in a small region of space. |
ZwsWjelzqDA-012|I'll say a box of length L, and the particle has to be between here and here. |
ZwsWjelzqDA-013|It'll have a wavelike property, so I'll draw a wavelike expression on this box. |
ZwsWjelzqDA-014|Now, this wavelike expression I'll call the wave function of that particle. |
ZwsWjelzqDA-015|The wave function of that particle will give the designation psi, in this case psi of x because this is the x dimension in space. |
ZwsWjelzqDA-016|Now, we've already said that the intensity of the wave squared is going to give us indication of the probability of finding the particle. |
ZwsWjelzqDA-017|So the probability size squared gives us the probability of finding the particle. |
ZwsWjelzqDA-018|Clearly in this case, the probability of finding the particle right in the middle of the box would be very high if this particle behaves like a wave. |
ZwsWjelzqDA-019|Well, how do I come up with these wave functions? |
ZwsWjelzqDA-020|Well, I can actually do some mathematics. |
ZwsWjelzqDA-022|And when I do those things, I can solve the differential equation for the particle stuck in this tiny little box. |
ZwsWjelzqDA-023|It's behaving like a wave. |
ZwsWjelzqDA-024|There are those wave functions psi. |
ZwsWjelzqDA-025|These are how the wave functions psi must interact with each other if it's a particle to be stuck in this box. |
ZwsWjelzqDA-026|Now, we won't go through all the mathematics, but you can solve this. |
ZwsWjelzqDA-027|And when you solve this equation, you get an expression for psi. |
ZwsWjelzqDA-028|It's not that hard to understand. |
ZwsWjelzqDA-029|And it looks like a wave function. |
ZwsWjelzqDA-033|There's not just one solution to this expression. |
ZwsWjelzqDA-034|There's multiple solutions. |
ZwsWjelzqDA-035|All the integers n work and give you a solution to this equation. |
ZwsWjelzqDA-036|So that means there's not one wave function that works. |
ZwsWjelzqDA-037|There are several wave functions that work. |
ZwsWjelzqDA-038|You can have a ground state, the smallest value of n, but you can have what we call excited states. |
ZwsWjelzqDA-039|Higher values of n also give wave functions, and you can tell what happens. |
ZwsWjelzqDA-043|We can also say, well, what's the energy of that particle? |
ZwsWjelzqDA-044|We can calculate the energy using our expression for the wave function and the probability squared. |
ZwsWjelzqDA-045|And we can say, well, I'll rank the energy. |
ZwsWjelzqDA-046|These particles increase in energy as n increases. |
ZwsWjelzqDA-048|The length of the box, the quantum number, Planck's constant are all in there. |
ZwsWjelzqDA-049|So I can then plot out, well, the lowest energy state n equal 1. |
ZwsWjelzqDA-050|We have no n equal 0 state. |
ZwsWjelzqDA-051|N equal 1 is where we start our counting. |
ZwsWjelzqDA-052|N equal 2, higher energy state. |
ZwsWjelzqDA-053|You'll see n goes in as the square, so higher n, higher energy state. |
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