 In this video we are going to discuss the nature of the compounds formed by the group 14 elements. We will also see how the presence of d orbitals affect the chemistry of these elements. From the previous videos we have seen that one of the characteristic features of the group 13 elements was that they were electron deficient in their trivalent state, right? And because they are incomplete octa, their compounds could act as Lewis acids by accepting electron pairs from electron to species and forming complexes or adducts. Now based on this, what can you comment on the nature of the group 14 elements? In their group oxidation state which is plus 4, would the compounds of these elements act as electron rich or electron deficient species? So pause the video and think about it for a moment. So in order to answer that, we need to see if the central atom in a molecule gets an octet configuration. Okay, so let's take the example of carbon here. As the element has 4 valence electrons, they can combine with other elements, let's say x by sharing of these 4 valence electrons. And what do you see? We can see that here we get an octet configuration. That is a central atom now has 8 electrons around it. So here we have taken the example of carbon but just like carbon all of the group 14 elements attain stable octet configuration in their plus 4 oxidation state. So we can conclude that in the tetravalent state the group 14 compounds are not electron deficient or electron rich but they are electron precise compounds. That is they have precisely 8 electrons around the central atom. But there's an interesting caveat to this trend. You see, we would expect that since they're electron precise or have completely satisfied octet, they would remain neutral and would have no desire to take up more electrons. And you're absolutely right, they would be neutral. But the thing is that some of the elements in this group 14 that is basically all of the elements except carbon can still accept extra electron pairs and exceed their covalence beyond 4. Now you might be wondering how is it possible because here you have completely satisfied octet. So where will these extra electron pairs go? Well they would go into the MTD orbitals. You see except carbon all other elements can expand their octet due to the presence of MTD orbital. There is no 2-day orbital in the second shell so carbon cannot expand its octet here. But silicon, you can see it has 3D, here we have 4D and tin has 5D and so on. So basically all the other elements have extra MTD orbitals in them. And that means they are capable of accepting extra electron pairs and can end up forming complexes. For example, it is very common to observe the prevalent compounds of group 14 elements like CF4, SIF4, GCL4, SNCL4 and even PBCL4. But when we talk about expanding the covalence beyond 4, not all of the group 14 elements can do it. Only those elements which have MTD orbitals are able to expand its covalence beyond 4 and form complexes as shown here. Since carbon has no such diorbitals present, you cannot observe any such complex formation. And because of this their halides are also able to undergo hydrolysis reaction where they react with water and accept the lone pair of electrons of the oxygen atom of water into their MTD orbitals. So to understand this, let us look at the reaction between silicon tetra chloride and water. Now the outer electronic configuration of silicon is 3S2, 3P2, right? That means it has the presence of MT3D orbital. And it is this MT3D orbital that accepts a lone pair of electrons from the oxygen atom of water. And when that happens, water breaks this SICL bond one by one and replaces it with hydroxyl group as you can see here. Now the final product of this hydrolysis reaction is nothing but silicic acid. This on heating will give you a white solid of silicon dioxide. In fact, SICL4 reacts violently with water and a lot of heat is produced in this reaction. And when you perform this in the laboratory you will see that because of the heat the water added actually begins to boil and start forming bubbles. So again the reason why SICL4 is easily hydrolyzed by water is because the central atom silicon here can accommodate the extra lone pair of electrons from the oxygen atom because again due to the presence of the 3D orbital. Right? Another reaction would be the reaction of lead tetrachloride with water where it again undergoes hetals as reaction to form lead oxide and hydrogen chloride gas. Now if you compare it with carbon you can see that carbon tetrachloride does not react with water at all. Carbon has no MTD orbital which the lone pair of electrons can occupy. In fact in the laboratory if you mix these two together you will see that they form two distinct layers. On the top you find water layer and on the bottom you will find the carbon tetrachloride layer. So this is because these two liquids are completely immiscible with each other and they do not react at all. So to summarize what all did we discuss in this video? Well we saw that the group 14 elements form electron precise compounds. That means the central atom in a molecule has exactly or precisely 8 electrons around it. We also saw that because of the presence of D orbitals certain elements in the group 14 are able to expand their valency beyond 4. And as a result the halides of their elements are able to undergo hydrolysis reaction and also form complexes by accepting electron pairs from electron rich species.