Using the shorthand notation of Figure 22.9, draw the structure of the cyclic silicate anion in which four SiO 4 tetrahedra share O atoms to form an eight-membered ring of alternating Si and O atoms. Give the formula and charge of the anion.

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.

Ch.22 - The Main Group Elements

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McMurry 8th Edition

Ch.22 - The Main Group Elements

Problem 22.100

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Chapter 22, Problem 22.100

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.

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Identify the basic building block of silicate structures, which is the SiO_4^{4-} tetrahedron.

Understand that in cyclic silicates, these SiO_4 tetrahedra share oxygen atoms to form rings.

Visualize the structure: four SiO_4 tetrahedra sharing oxygen atoms to form an eight-membered ring, alternating between silicon (Si) and oxygen (O) atoms.

Determine the formula by considering the number of Si and O atoms in the ring. Since each tetrahedron shares two oxygen atoms with its neighbors, calculate the total number of oxygen atoms in the ring.

Calculate the charge of the anion by considering the charge of each SiO_4^{4-} unit and how sharing oxygen atoms affects the overall charge.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Cyclic Silicates

Cyclic silicates are a class of silicate minerals where silicon-oxygen tetrahedra are linked in a ring structure. In these structures, each tetrahedron shares two of its oxygen atoms with neighboring tetrahedra, forming a closed loop. The arrangement can vary in size, and the cyclic nature influences the physical and chemical properties of the silicate.

Silicon-Oxygen Tetrahedron

The silicon-oxygen tetrahedron is the fundamental building block of silicate minerals, consisting of a central silicon atom surrounded by four oxygen atoms at the corners of a tetrahedron. This tetrahedral arrangement allows for various bonding configurations, leading to diverse silicate structures, including chains, sheets, and rings, depending on how the tetrahedra are linked.

Anion Charge and Formula

The charge of an anion is determined by the balance of the total negative charge from the oxygen atoms and the positive charge from the silicon atoms. In the case of cyclic silicates, the overall charge can be calculated based on the number of tetrahedra and the shared oxygen atoms. The formula typically reflects the ratio of silicon to oxygen, indicating the structure's composition and charge.