Atomic Radius & Density of Transition Metals - Video Tutorials & Practice Problems
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Atomic Radius
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Now recall that when it comes to atomic radius of main group elements, it's going to decrease from left to right across a period and going up a group. And when it comes to transition metals, though it could, it's gonna follow the same general trend, but change in size is more gradual. Now, what's the reason for this? Well across a period, the number of outermost electrons which is some shell number, which we're gonna use the principal quantum number N. And then these transition metals have an outer shell which is in the S orbitals and they can have one or two electrons involved. You will put two electrons and that's gonna be constant. So for example, we're taking a look here, we say that the general trend again is it decreases as we head towards the right top portion of the periodic table. Here, we have our transition metals that we're paying attention to. We're only paying attention to rows 45 and six, period seven or row seven is more unpredictable because it's more synthetically made elements, heavy elements. Their behavior is not easy to describe. So we're gonna leave out the seventh row if we're looking at rows five and six, in particular, we can say that we know that the atomic radius decreases as we head up a group. But if we're comparing their atomic radiuses here, we can see that in some cases, they stay the same. And in other cases, they only decrease slightly. If we were to take a look at TC and re here TC. If we were to write its electron configuration, we'd have krypton 45 5 S two. And then re rhenium would be xenon 4, F-14 5 D uh 56 S two. We see that they're outer shells. For TC is in the fifth shell has two electrons in the outer shell. Here is two electrons in the sixth shell. The electrons that we're adding in are getting added to either D or F orbitals which are in the inner shells, the outer shells staying the same, we're just packing in more electrons in the center or in the shells that are closer to the nucleus. Because the outer shell is staying constant in size. We just see small variable changes in our atomic radius between the transition metals. Again, this change of atomic radius is more prominent amongst main groups elements and it's only a gradual uh change within our transition metals. And again, that's having to do with us having a constant number of electrons in the outer shell. And later on, we learn about other phenomenons that result in this gradual change in our atomic radius.
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example
Atomic Radius and Density of Transition Metals Example
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Which element from each pair would you expect to have the biggest atomic size? So remember, atomic size, atomic radius. As we head towards the top right corner of our periodic table, we should expect it to dec decrease. So if we take a look at the first one, we have N I versus T I nickel versus titanium titanium. If you look at your periodic table, it's more to the left than nickel. So titanium would be larger for the next one. We have TC. And RU again, take a look at the periodic table. Look to see where do you see them TC is to the left more so than RU. So TC would be larger. Next, Rh and MB again, take a look at your periodic table. Look and see where you find each of these elements. NB is more to the left again than Rh. So NB would win. And then we have Y and A G yum versus silver. Again, which one is more to the left, yum would be more to the left. So Y trim will be the larger out of these pair. So here we've identified which element in each pair would have a larger atomic radius. Again, as we head towards the top right corner, we expect our atomic radius to decrease. So if you want the larger element look which one is more to the left and lower down, these would result in larger atomic radii.
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concept
Lanthanide Contraction
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Now, when we look down a group, we can say that periods 5 to 6 of transition metals have relatively constant size. Now, this is due to what we call the Latin night contraction. Now, according to the Latin night contraction, we're gonna have an increase in our effective nuclear charge which is Z sub eff and that's due to four F sub shots, these four F electrons yield poorly remember effective nuclear charge itself is just the attractive force between our nucleus and the surrounding electrons. We're gonna say that recall that if we increase the number of electrons in a shell, this is gonna increase our attractive force. So just imagine that you are adding additional electrons as you go from trend from period five to period six. What are we adding or adding electrons in F orbitals? The shell number is not increasing. Those f orbital electrons are going into our inner shells which are closer to the nucleus. You're packing in more electrons, you're adding more protons to your nucleus. There's gonna be a greater attraction between those protons in the nucleus and those surrounding electrons, those F orbital electrons. This causes an increase in our effective nuclear charge, pulling them closer and thereby causing your overall atomic signs of your element to contract just slightly. So here this is gonna cause a decrease in expected atomic size of period six transition metals. So basically, once you introduce your f orbital electrons without increasing the shell size, you're just causing more of an attractive force between your nucleus protons and your surrounding electrons. Now, here if you want a refresher in terms of this, make sure you take a look at our periodic trend under effective nuclear charge. For more information here, we just have an example of our nucleus which has our protons and our neutrons. And then we have these different shells. We're starting off by looking at the fourth shell because that's where we first have the introduction of our f orbital electrons packing them in causing a greater attraction between my nucleus here and the f orbital electrons that I'm adding. So just remember when we're looking down a group, we have this Latin night contraction, which is supported by the introduction of F orbital electrons.
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Atomic Radius and Density of Transition Metals Example
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In this example question, it says which of the following transition metals would you expect to be larger but are actually same or nearly same size at as techni Well, if we look on our periodic table, we have tech num which is in period five. So if we look just one row down below it in period six, we have rum. Remember we saw that radium and tech medium have similar atomic radius. That's because of the lenite contraction. When we go into the sixth period of the periodic table, we have the introduction of f orbital electrons. The intro introduction of more of these electrons into one of our inner shells causes a greater attraction between those electrons and our more positive nucleus. This is termed our effective nuclear charge. OK. So here option D would be our final answer.
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concept
Density
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Now, when it comes to the density of our transition metals, just remember that increases as the mass of the metal increases, we're gonna say an increase in density down a group is more significant then across a period. And we're going to say here that the general trend is as we had from the left to the right side of our periodic table in relation to our transition metals. In this case, our density is going to increase. And that's because our mass is increasing. And then we're gonna say as we head down a group, our mass also still increases. Now, remember as we're heading across a group, our size is staying relatively constant because we're just adding additional electrons to either our D or F orbitals. So our volume is staying more the more or less the same density equals mass over volume. So your volume is staying more or less the same, but your mass is increasing. This causes an increase in your density. If we're looking at going down a group, well as we're going down a group, our mass is still increasing because we're going from lighter elements of top to heavier elements on the bottom and then we have lamp contractions that are possible. So that kind of keeps your volume more or less close to the same as you're heading down a group. So again, your, your volume is staying relatively the same, your mass is increasing greatly. This also causes an increase in your density. So just remember the formula for density, remember with our transition metals because of we're being in the same row or because of the lain night contraction, our vine is staying more or less the same but our mass is increasing. This causes an overall increase in our density.
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Atomic Radius and Density of Transition Metals Example
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Hey, everyone. So in this example question, it says, identify transition metal with the highest density. So remember our density is going to increase as our mass increases. And also remember that there's gonna be a greater spike in density as we go down a group than going across a period. So going down a group, there's more significant increase in our density. If we take a look here at our options, we'd say here that A and B represent transition metals that are gonna be in period four. And if we look at C and D, well, they represent elements that are in period six since C and D are lower down in terms of groups, they're in row six, their densities are gonna be more impactful. They're gonna have a more significant higher value. So that means A and B are out. Now, here we look at C versus D. Remember the general trend is as we head towards the right across a period, our density increases and as we go down a group, our density increases, Osmium C is more to the right than option D. So Osmium would have a larger density. So here my answer would be option C. So just remember we look and see where they are in relation to each other. On the periodic table, the ones lower down in the group would have a more significant higher density than the ones higher up a group. That's what eliminated A and B. And then to break the tie between C and D, just remember more towards the right of the periodic table equals a higher density giving us option C as our final answer.
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