 I'm going to go through this practice test, make a video about it. It's going to probably be fairly long, but it should be good for you. And I know a few of you may look at it, may make it worthwhile to get a few grades up. I'll pull up the class average on this thing. All right. So let's take a look at our questions here. First question, how many protons are in the isotope carbon-14? Now we have to remember what these two little numbers next to the isotope symbol mean. The number on top is the mass, and the number that's on the bottom is the atomic number. This question is asking about protons. So the number that we would use is the atomic number, and we would say it has six protons in it. Atomic number is always the number of protons that never changes, so we can count on that for the normal atoms, the isotopes, or the ions. Next question, another isotope symbol. Again, the number on top is the mass, and the number on the bottom is the atomic number. But this time it asks for neutrons. And anytime we're doing neutrons, it's going to be mass minus atomic number. We will not use a periodic table to do this because we already have the mass and the atomic number. All we have to do is subtract the two, and there would be four neutrons there. So expect some questions on that quarter exam about interpreting isotope symbols and describing protons, neutrons, maybe electrons. Remember electrons are the same as protons, as long as it's neutral. But protons and neutrons, I think, are your two big things. I hope anyways. All right. Let's move on to the next question. And the next question about Rutherford's Goldfoil Experiment. They say that you need to know what the results of the Goldfoil Experiment told Rutherford and how that changed the model of the atom. Remember, up to this point we had the Plum-Pudding Model. The Plum-Pudding Model said that an atom was a massless cloud of positive charge with electrons scattered through it, like chocolate chip cookies, where the cookie is the cloud of positive charge and the chocolate chips are the electrons. Now he shoots these alpha particles at the Goldfoil, sees what happens, and he notices a small number of alpha particles bounced off. And the question is, what does that tell him about it? Well, it wouldn't be this. It wouldn't tell him that the atom was a large solid sphere, because if that were the case, they'd all bounce off. It wouldn't tell him, see, that electrons are scattered through a cloud of positive charge, because if that were the case, there's nothing in there for alpha particles to bounce off, and again, they'd all go straight through. And we know it's not D either, because the nucleus does not contain negatively charged particles. That's not part of Rutherford's model. The answer is B. Those particles that back-scattered, that bounced off, were hitting the relatively massive, but very, very small nucleus in the center. Again, make sure you familiarize yourself with Rutherford's experiment. Look back to the notes. Make sure you know what little things told him. That's part of the standards, and there will be a question on it. Number four, what do the following elements have in common? So we have calcium, or calcium carbon, silicon, germanium, tin, and lead. These are all members of Group 14. All the members of Group 14 have four valence electrons. So they have the same number of valence electrons. Remember groups? Elements in a group have the same number of valence electrons. And in a period, they have the same number of energy levels. Potassium, calcium, nickel, arsenic, bromine, potassium, calcium, nickel. These are all same period ones here. If they're all in the same period, they all have the same number of energy levels. Groups are vertical columns. Groups are all about the valence electrons. Periods are horizontal rows. They are all about the number of energy levels. On to the next page, which of the following elements would shrink when they form an ion? This is periodic trend stuff. Periodic trends were electronegativitization, energy electron affinity, atomic radius, and ion size. And we learned about it in terms of the periodic table. We talked about how when you look at fluorine, fluorine has the highest electronegativity, highest electronefinity, highest ionization energy. And that's all because of the reactive elements. It's the smallest one. And we said Frantzium down here in the opposite corner has the lowest ionization energy, lowest electronefinity, lowest electronegativity because it's the largest atom on the periodic table. Those are the trends where I had three things here. I'd look and see which one's closer to fluorine if I'm looking for higher. I see which one's closer to Frantzium if I'm looking for lower. But this one doesn't use that trend. This is just the ion thing. And I said, what you have to know about this is that metals shrink, nonmetals expand. So this is asking us which one would shrink. Metals shrink, magnesium's the only metal on that list. Largest atom. Again, when we look at the periodic table, periodic trends, Frantzium has the lowest ionization energy, lowest electron affinity, lowest electronegativity because it is the largest atom. So the question here is really, which one's closest to Frantzium? B-E-S-R-M-G-C-A, B-E-S-R-M-G-B-A, B-E-S-R-M-G-C-A. B-E-S-R-M-G-C-A is the closest one. If we didn't have B-A, we had B-E. So it's these four that I gave you. Strawnium's the closest to Frantzium. So it would be the largest atom. It's furthest down the group. That means it has the most energy levels on it, and that's really what makes it the biggest. The next one's Sulfur Aluminum Sodium Magnesium. Sulfur Aluminum Sodium Magnesium. We're looking for smallest this time. Again, fluorine's the smallest. So it's the one that's closest to fluorine here, which would be the sulfur. And the reason why sulfur is the smallest is because it has the most protons in its nucleus. That gives us the strongest attractive force on its electrons, drawing the whole electron cloud in closer. Now this I didn't cover in class. I didn't cover in class. There's only one question about it. So here's how it works. This is a mass spectrum. It shows the number of isotopes that particular element has. So this one has two isotopes, an isotope with a mass of six, and an isotope with a mass of seven. The larger this peak, the more abundant it is, the more of it you have. So there's a lot more seven than there is six. When we do the mass on the periodic table, it's a weighted average of these two things. So being that there is more at the mass of seven, it tells us that the mass on the periodic table is gonna be really close to seven. So we just take our periodic table out and we look for the element that has the mass really close to seven. And that's like, this would be a mass spectrum for lithium. Again, each peak represents an isotope. It tells us here what the masses are. I put them in here because they're kind of hard to read. There's a peak at six and there's a peak at seven. So most of it is at seven, very little bit at six. If I average that together, I'm gonna get a number that's really close to seven. So I'm just looking on the periodic table to find the element where the mass is really close to seven. This is another question, similar concept. The atomic mass of Brillium is 9.0122. Well, what that's telling us is that most of the barium, the average atom is nine. Whatever that mass is closest to, because it's a weighted average, because of the way it's calculated, whatever that mass is closest to is going to be the most abundant isotope. So when you see 9.0122, you round that to a whole number, that's gonna be your most abundant atom. That's gonna be your most abundant isotope. All right, orbital diagram for oxygen. You have to be able to pick the right one. Oxygen is atomic number eight, which means we are going to have eight electrons in it. And if you look through all of these, they all have eight arrows. So they all have the right number of electrons. What's gonna differentiate between the right and the wrong is whether or not they're put in the boxes correctly. Again, S's only hold two, P's can hold up to six, and the S's aren't usually an issue. It's an up and a down. It's the P's that we have to be careful about. And the rules for putting the arrows and the P orbitals is that you have to put one on each blank first, and then you're allowed to double them up. So we're dealing with two P, and as you can see, there's four in it. Two four, two four, two four. They all have four in it. The correct way of doing four would be like this. One in each blank first and then double it up, which means provided these are both pointing up and it's kind of hard to see. They don't give me paper to make photocopies. So I'm assuming those are both up, that's up, that's down, that's up, that's down, that's up, that's down. I'm assuming those are both up. But that would be the correct one there. And on to the backside. Now, these are the shapes of the orbitals that I told you about. S orbitals are sphere. You can think S sphere, just makes sense. P's are dumbbell shaped, and D's look like four leaf clovers. So we know that that's an S orbital, that's a P orbital, and that is a D orbital. The question's asking where the last three electrons in the phosphorus atom would be. Well, we need an electron configuration. Phosphorus is atomic number 15, so we gotta put 15 electrons into the electron configuration. We start with one S, we can put two there. The next orbital is two S, we can put two there, that's four, we still got 11 to go. Next orbital is two P, P's can hold six. Now we're up to 10, we have five, we have, yeah, five more to go. Next two will go in three S, so now we have three left. Next orbital up would be three P, and it would only be three not six. The last three will go in three P, P orbital. That's a drawing of a P orbital, so B is the answer. You would use the electron configuration to figure out where the final electrons were going, and then you'd have to know the shapes to pick what that last orbital is, and again that last orbital is a P orbital in this one. All right, moving on to the next one. What will be the electron configuration of oxygen, sulfur, and selenium all have in common? Well, oxygen has eight electrons, that would be one S2, two S2, two P4. Two P4, two plus two is four plus four is eight. Sulfur has 16, so it's like the phosphorus, but with one more in it. So it'd be one S2, two S2, two P6, three S2, and in the end it's gonna be three P4. Well, there it is. I can see what they have in common. They all end in P4. If I did selenium, and it would be a much longer one, it would also end in P4. You can figure that out by knowing the blocks on the periodic table, and this is the P block. That would be P1, P2, P3, P4. They would all, everything in that column would end in P4. All right, next one, wavelength and frequency. Assuming they have the same velocity, the way this works, long wavelength means low frequency, short is high. Longest, low, short is high. And it's asking for the highest. So we want the shortest, which would be E. Remember, wavelength is crest to crest, or trough to trough. This one here, the longest one would be the lowest. This one here, the shortest one would be the highest. More electron configuration fun, which is the correct electron configuration for a sulfur ion. Well, we already have the electron configuration for sulfur, it's right here. Again, one S2, two S2, two P6, three S2, three P4. That's the normal electron configuration for sulfur. If you have trouble with those, there's a whole video I put up about electron configurations. Now sulfur's in group 16, which means sulfur has six valence electrons. It's a non-metal. And non-metals want to gain electrons to become stable. They have to gain what they need to have eight. Sulfur has six, it needs two more. If we were to add two more electrons to the configuration, it would go right here on the end, changing the four to a six. Remember, in most cases, an ion is going to end in S2s and P6s. So we're gonna pick the one that matches that, which is C. Sodium, just plain old sodiums electron configuration. Sodium's atomic number 11. First two electrons go in, one S. Next two electrons go in, two S. Next six electrons go in, two P. Two plus two is four, plus six is 10. We have one more to go. It'll go there in three S. So VC answer. Make sure you can work with the neutral atoms in the ions. If you're doing the ion, you'll start off with the neutral configuration. And then what you'll do is look at the periodic table, figure out if it's a metal or a non-metal. Remember, metals lose, non-metals gain. So if it's a metal and it has one valence electron like sodium does, it would have to lose that to become stable. And you would just take the three S one off the end. If it's a non-metal, it's gonna gain electrons to become stable and you'll just add enough to have eight. And it'll most likely end in P6. All right. Didn't talk about them much because I don't like playing trivial pursuit. Mendelev does the first periodic table and it's all based on mass that mostly comes along and discovers the atomic number. And that's where everything changes in the modern periodic table is raised by atomic number now. So if it's a Mendelev table, it's all arranged by the mass of the atoms. If it's a Mosley based table, it's all based on atomic number. Our modern one is based on atomic number. Good enough. Covered. These are emission spectrum. These are the things that Bohr used to identify energy levels. We have a mixture here. It's a mixture of some two of those gases and we gotta figure out which one. And there's a couple of things we can look for. This line is a giveaway. There's only one gas that has a line that low and that is gas A. So we know gas A has to be a part of our mixture. The other giveaway here lies in the double lines. We have a double line that goes up that far. It's quite far over to the right here and there's only one other gas that has a double line that far over and that's D. So our mixture is gases A and D. Moving on. Number 19, how many total electrons are transferred from calcium to nitrogen in the compound calcium nitride? Now the first thing I wanna do is figure out what calcium nitride is. Calcium is just calcium, no problem there. Nitride, IDE is just playing on nitrogen, tells us that. And calcium's in group two, that's a plus two oxidation number. Nitrogen's in group 15, that's a negative three. Two goes there, three goes there. C, A, three, and two is the formula. So I have three calcium's here that are gonna be transferring electrons or giving up electrons. Now the next thing I gotta know is how many they're gonna give up. Calcium is in group two, which means it has two valence electrons to lose. So each of these three calcium atoms has to lose two electrons for a total of six. And again, this question's asking for total electrons that are being transferred. So the total electrons that'd be transferred here would be six. Now the next one I wrote differently because I don't know how they're gonna ask this. If they're gonna be based on totals or if it's gonna be based on each. What will happen to each sulfur atom when the compound sodium sulfide is formed? Let's review the crisscross here. Sodium is Na, group one plus one. Sulfide is sulfur, sulfur's in group 16. It's a negative two. One goes there, two goes there. Na2S, there's sulfur. It's gotta receive all the electrons from the sodium. Sodium is in group one, which means it has one valence electron. There are two of them. So there are two electrons in all that have to move from here to here. That have to move from the sodium to the sulfur. So being only one there, each sulfur will gain two electrons. Which is what sulfur has to do anyways. The other side of looking at this is to look at sulfur on the periodic table. Sulfur's in group number 16. It has six valence electrons. Because it's a non-metal, it has to gain what it needs to have eight. If you got six, you need two more. So you can answer it either way. You can even go as far as drawing the Lewis structures for this. Sodium looks like that. Sulfur looks like that. I get one transferred over, but that's not enough. I still got another single dot down here. So I draw in another sodium, bring it there. Sulfur receives two electrons. There's a number of ways of coming up with that answer. And the last one on this particular paper. Structural formula for SiO2. So silicon's got four valence electrons. Group 14 looks like that. Oxygen in group 16 with six valence electrons. Looks like that. Start pairing up single dots. I got a double bond between that oxygen and sulfur. I've got a double bond between that oxygen and sulfur. The only one that shows that is C. And the other way to figure this out is if you know carbon dioxide, CO2 looks that way. Silicon and carbon have the same Lewis structures. So they are gonna have the same structural formulas as well. Three atom linear. And again, the reason why it's linear is because there's no one shared electrons on that metal atom. Whole video of about that too. So if you need to watch that, watch that. This is gonna be a marathon video. Moving on to the next page. This is an interesting one. We talk about resonance. And I'm looking at the way that they say you have to know resonance. It's just, I don't care. I don't know. They say that you have to be able to pick out the resonance structures for a polyatomic ion like sulfate. Now the first thing we wanna do is check our list of polyatomic ions. Sulfate, A-T-E is S-O-4. So we need the one that shows S-O-4 in it, which automatically excludes B. I mean, yeah, because that's S-O-3. It automatically excludes that. Because that's S-O-3. And automatically excludes that. Only answer's A. Hopefully it'll be that easy. I mean, you're not supposed to be able to draw these structural formulas. That's what we were told anyways. So I'm hoping that you can just simply look at the formulas of these. That's one sulf for three oxygens. So that would be S-O-3. That's one sulf for three oxygens. So that would be S-O-3. That's one sulf for three oxygens and a hydrogen. So that's H-S-O-3. So the only one that actually has the formula S-O-4 is this one. So hopefully it'll be able to use that kind of process of elimination to figure out which is the correct resonance formulas. If not, it's only one question. So hopefully it won't hurt you too bad. Number 23, which of the following would be the correct structural formula for NH3? Start with the Lewis structures. Nitrogen looks like that. Hydrogen looks like that. Four atoms is to the trigonal planar, which would be this. Or it's pyramidal, which would be that because of those two dots there. It's pyramidal. That deforms the structure and makes the tiny pyramid. All right. Move it on. This thing here, one carbon, one, two, three, four chlorines, five atoms. There's only one shape of five atom molecule can be. That is tetrahedral. It was.