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Ch.13 - Solids & Modern Materials

Chapter 13, Problem 50

An oxide of rhenium crystallizes with the unit cell shown here (rhenium=gray; oxygen=red). What is the formula of the oxide?

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Hey everyone, we're asked to determine the formula of a solid that crystallizes with the following arrangement with a being are red and B being are blue. So first let's go ahead and count the red spheres in each corner of the cube. So we have one, aN:aN:000NaN and eight. So we have 88 atoms in our corner and each atom in a corner contributes 1/8 Unit Contribution. So when we multiply these two values, our AIDS cancel out and we end up with a single A. So an A. Adam has one unit. Now let's go ahead and look at our blue spheres. Now when we look at our blue spheres on the edges of our cube, we find that we have one, two, three and four. So we have four B. Adams At the edges of our Cube. So the unit contribution for this is going to be 1/4 of a unit. So when we multiply these two values together our forest cancel out and we end up with a single unit for B. So this means overall formula for our solid is going to be a B. Now, I hope this made sense. And let us know if you have any questions