Which of the group 4A elements have allotropes with the diamond structure? Which have metallic allotropes? How does the variation in the structure of the group 4A elements illustrate how metallic character varies down a periodic group?

Video transcript

Welcome back, everybody. Here's our next question. Among the group four A elements, only carbon has an allotrope with a diamond structure. While the rest have metallic allotropes is this statement true or false if it is true, justify your answer. If otherwise state the correct answer a true. This is because carbon is the only non metal in group four A elements. Choice B true. This is because diamond structure is a characteristic of carbon allotropes. Only choice C false. The elements C SI and GE can have allotropes of the diamond structure. While SN and PB have metallic allotropes or choice D false the elements C and SI can have allotropes of the diamond structure while Gesn and PB have metallic allotropes. So let's recall what a diamond structure is versus a metallic allotrope. These are both solid forms of these elements. We're talking about a single group of elements and we have a diamond structure which is a large covalent network. So not just individual molecules with covalent bonds, but an entire lattice work or network all joined by covalent bonds. So we have all carbon atoms joined by those covalent bonds where they're sharing electrons between atoms, this is opposed to metallic allotropes as we know, a characteristic of metals is that they lose electrons completely. So in a metallic allotrope, we have a lattice was the solid form with delocalized electrons, our metals lose electrons completely. They become ionized. And in this solid form, you have this lattice where the electrons can move around. This is key to the conductivity of metals since those electrons are delocalized. So let's think about what would make an element form a covalent network versus a metallic lattice. Well, since we're all in a single group, we need to think about the metallic character as you go up or down the periodic table. So mental character increases, going down the periodic table due to increasing atomic radii. So as the electrons get further and further away from the nucleus, they're farther away from that positive charge and they're increasingly shielded from it by the inner electrons. So since metals are characterized by losing electrons, those increasingly distant and shielded electrons can be lost more easily. So within our group, let's think about the order of our elements, we have carbon up at the top silicon below it. Then Germanium ge, then tin sn, then PB L we do have underneath it, the element fl which is one of those super heavy elements, but we don't know much about it. It's one of those that just exists very briefly and it's not mentioned in our answer choices. So we're not going to worry about it. We're all the way over in group four A. So we wouldn't expect all of these to act as metals. We know that the metallic elements tend to be over in groups one A and two A and indeed, we have carbon, which of course is a non metal. But then silicon and germanium are semi metals. So they have more metallic characteristic than carbon, but they can act either way as a metal or a nonmetal depending on what kind of interactions they're having. And then tin and lead as we probably even know just from common life are both definitely metals. So with that in mind, let's look at our answer. Choices. So first we have to determine true or false, only carbon has an allotrope. Well, we know that silicon and Germanium are semi metals. So as we might expect from that, all three of these carbon, silicon and germanium can have diamond allo tropes, they can have this structure because they can form covalent bonds since they aren't completely metallic. So our statement here is going to be false. It is not just carbon, it's all three of the top elements. So that's going to eliminate choice A and B which both say true. When we look at choice A, it says this is because carbon is the only non metal. Well, that part is correct, but it's not a true statement. So choice A is wrong and choice B true because diamond structures, characteristic carbon allotropes only as we said, that is not true. So we know our answer is false. So we're looking at C and D but we have to then state the correct answer. So C says after false, the elements, carbon, silicon and germanium can have allotropes with a diamond structure. That's correct. While tin and lead have metallic allotropes, that is correct also. So we'll go ahead and select choice C as our answer. But to be thorough, take a look at choice B so it correctly says false and then says the elements, carbon and silicon can have allotropes with a diamond structure. While Germanium tin and lead have metallic allotropes. Well, this is incorrect because Germanium is also a semi metal and can have that diamond structure. So that's why choice D is incorrect. So once again our statement here that only carbon has an allotrope with a diamond structure while the rest have metallic is false as it says in choice C. And the correct statement is that the elements C SI Nge can have diamond structure while SN and PB have metallic allotropes. See you in the next video.