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Ch.12 - Solids and Modern Materials
Chapter 12, Problem 38

Calculate the volume in ų of a face-centered cubic unit cell if it is composed of atoms with an atomic radius of 1.82 Å.

Verified step by step guidance
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Step 1: Understand the structure of a face-centered cubic (FCC) unit cell. In an FCC unit cell, atoms are located at each corner and the centers of all the faces of the cube.
Step 2: Recognize that in an FCC unit cell, the face diagonal is equal to four times the atomic radius (4r), because the face diagonal passes through the centers of two corner atoms and one face-centered atom.
Step 3: Use the relationship between the face diagonal and the edge length (a) of the cube. The face diagonal can be expressed as \( \sqrt{2}a \). Therefore, set \( \sqrt{2}a = 4r \) and solve for the edge length \( a \).
Step 4: Substitute the given atomic radius (1.82 Å) into the equation from Step 3 to find the edge length \( a \) of the unit cell.
Step 5: Calculate the volume of the cubic unit cell using the formula \( V = a^3 \), where \( a \) is the edge length obtained in Step 4.
Related Practice
Open Question
Iridium crystallizes in a face-centered cubic unit cell that has an edge length of 3.833 Å. (a) Calculate the atomic radius of an iridium atom. (b) Calculate the density of iridium metal.
Textbook Question

Calcium crystallizes in a body-centered cubic structure at 467°C. (a) How many Ca atoms are contained in each unit cell?

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Textbook Question
Calcium crystallizes in a face-centered cubic unit cell at room temperature that has an edge length of 5.588 Å. (b) Calculate the density of Ca metal at this temperature.
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Open Question
Aluminum metal crystallizes in a face-centered cubic unit cell. (a) How many aluminum atoms are in a unit cell? (b) Estimate the length of the unit cell edge, a, from the atomic radius of aluminum (1.43 Å). (c) Calculate the density of aluminum metal.
Textbook Question

An element crystallizes in a face-centered cubic lattice. The edge of the unit cell is 4.078 Å, and the density of the crystal is 19.30 g>cm3. Calculate the atomic weight of the element and identify the element.

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Textbook Question

Which of these statements about alloys and intermetallic compounds is false? (a) Bronze is an example of an alloy. (b) 'Alloy' is just another word for 'a chemical compound of fixed composition that is made of two or more metals.' (c) Intermetallics are compounds of two or more metals that have a definite composition and are not considered alloys. (d) If you mix two metals together and, at the atomic level, they separate into two or more different compositional phases, you have created a heterogeneous alloy. (e) Alloys can be formed even if the atoms that comprise them are rather different in size.

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