Using the shorthand notation of Figure 22.9, draw the structure of the cyclic silicate anion in which four SiO₄ tetrahedra share O atoms to form an eight-membered ring of alternating Si and O atoms. Give the formula and charge of the anion.

Video transcript

Hi, everybody. Welcome back. Here's our next question. What is the tetrahedron based shorthand notation for a cyclic silicate anion consisting of five si si 04 tetrahedron that form a 10 membered ring composed of alternating si and O atoms. What are the charge and chemical formula of the anion? So let's think about when we draw these tetrahedron based shorthand structures. Each unit is an si four tetrahedron. We have five of them. They have this 10 membered ring of alternating si and O atoms. Well, how are those indicated with these shorthand structures that would be with shared corners. Each shared corner indicates an O atom with bonds to the two silicons in the center of those two tetrahedron. So if we draw our five tetrahedron in a ring with one corner touching each touching the next I will have the correct structure. So I'll put that up real quick, please excuse the rather lopsided drawing. But you can see here each, we have 12345 shared corners and each of these representing oxygens shared between two silicons, alternating si and O atoms. Now, we need to figure out the charge and chemical forming of the anion. Well, in order to do that, we think again about our structure, we have five of the si 04 tetrahedron. So we know our chemical formula will begin with si five. Now we have to calculate how many oxygens we have and what the charge is. So we know that in these structures, each corner is an oxygen atom shared corners represent these oxygen bridges between silicon atoms and therefore have a zero charge. They have two bonds to silicon, two lone pairs, zero formal charge, the unshared corners which represent terminal oxygens have a negative one formal charge. So when we look at our structure, we know we have five shared corners, 15 next to shared corners. So how many unsured corners do we have? Well, as we go around our ring on the outside of our ring, there's a corner of each of our five tetrahedron, 12345. So we have five are on the outside. But then each of these represent a sort of pyramid shape. So each of these have this top point that is an unshared oxygen. So 12345 more. So we have a total of 10 unshared corners. Each one represents an oxygen. So we have 15 total oxygens si 5015. Now, what's the charge? Well, we know that our 10 unshared corners each have a negative one charge. So our charge here will be minus 10. So once again, we have our structure here, our ring of five tetrahedron, each of which touches at one corner to the next. And our chemical formula si 5015, negative 10 with negative 10 being the charge on our anion. See you in the next video.