Textbook Question
Silicon carbide, SiC, is a covalent network solid with a structuresimilar to that of diamond. Sketch a small portion ofthe SiC structure.
Ch.12 - Solids and Solid-State Materials
McMurry8th EditionChemistryISBN: 9781292336145
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Table of contents
- Ch.1 - Chemical Tools: Experimentation & Measurement170
- Ch.2 - Atoms, Molecules & Ions160
- Ch.3 - Mass Relationships in Chemical Reactions169
- Ch.4 - Reactions in Aqueous Solution199
- Ch.5 - Periodicity & Electronic Structure of Atoms102
- Ch.6 - Ionic Compounds: Periodic Trends and Bonding Theory92
- Ch.7 - Covalent Bonding and Electron-Dot Structures61
- Ch.8 - Covalent Compounds: Bonding Theories and Molecular Structure59
- Ch.9 - Thermochemistry: Chemical Energy122
- Ch.10 - Gases: Their Properties & Behavior155
- Ch.11 - Liquids & Phase Changes54
- Ch.12 - Solids and Solid-State Materials73
- Ch.13 - Solutions & Their Properties120
- Ch.14 - Chemical Kinetics98
- Ch.15 - Chemical Equilibrium125
- Ch.16 - Aqueous Equilibria: Acids & Bases110
- Ch.17 - Applications of Aqueous Equilibria147
- Ch.18 - Thermodynamics: Entropy, Free Energy & Equilibrium86
- Ch.19 - Electrochemistry154
- Ch.20 - Nuclear Chemistry96
- Ch.21 - Transition Elements and Coordination Chemistry156
- Ch.22 - The Main Group Elements187
- Ch.23 - Organic and Biological Chemistry51
Chapter 12, Problem 51
Cesium chloride crystallizes in a cubic unit cell with Cl- ions at the corners and a Cs+ ion in the center. Count the numbers of + and - charges, and show that the unit cell is electrically neutral.
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Identify the positions of the ions in the unit cell: Cl- ions are located at each of the eight corners of the cube, and a single Cs+ ion is located at the center of the cube.
Calculate the contribution of Cl- ions to the unit cell. Since each corner ion is shared by eight adjacent unit cells, each Cl- ion contributes 1/8 of its charge to the unit cell. Multiply the charge contribution of one Cl- ion by the number of corners to find the total charge contributed by Cl- ions.
Consider the contribution of the Cs+ ion. Since the Cs+ ion is located at the center and not shared with any other unit cell, it contributes its entire charge to the unit cell.
Add up the total charges contributed by Cl- ions and the Cs+ ion. Remember that Cl- has a charge of -1 and Cs+ has a charge of +1.
Verify that the sum of the charges equals zero, demonstrating that the unit cell is electrically neutral.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Ionic Compounds and Charges
Ionic compounds are formed from the electrostatic attraction between positively charged cations and negatively charged anions. In the case of cesium chloride (CsCl), cesium (Cs+) is the cation with a +1 charge, while chloride (Cl-) is the anion with a -1 charge. Understanding the charges of these ions is essential for determining the overall charge balance in the unit cell.
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Ionic Compounds Naming
Unit Cell Structure
A unit cell is the smallest repeating unit in a crystal lattice that reflects the symmetry and structure of the entire crystal. In the cubic unit cell of cesium chloride, Cl- ions occupy the corners, and a Cs+ ion is located at the center. Recognizing the arrangement of ions within the unit cell is crucial for analyzing the charge distribution and confirming electrical neutrality.
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Electrical Neutrality in Crystals
For a crystal to be electrically neutral, the total positive charge must equal the total negative charge. In the CsCl unit cell, there are eight Cl- ions at the corners, each contributing a -1 charge, and one Cs+ ion in the center contributing a +1 charge. By calculating the total charges, one can demonstrate that the unit cell maintains electrical neutrality, as the total charge sums to zero.
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Related Practice
Textbook Question
If the edge length of an NaH unit cell is 488 pm, what is the length in picometers of an Na¬H bond? (See Problem 12.50.)
Textbook Question
If a protein can be induced to crystallize, its molecular structure can be determined by X-ray crystallography. Protein crystals, though solid, contain a large amount of water molecules along with the protein. The protein chicken egg-white lysozyme, for instance, crystallizes with a unit cell having angles of 90° and with edge lengths of 7.9 * 103 pm, 7.9 * 103 pm, and 3.8 * 103 pm. There are eight molecules in the unit cell. If the lysozyme molecule has a molecular weight of 1.44 * 104 and a density of 1.35 g>cm3, what percent of the unit cell is occupied by the protein?
Textbook Question
Carbon and oxygen combine to form the molecular compound CO2, while silicon and oxygen combine to form a covalent network solid with the formula unit SiO2. Explain the difference in bonding between the two group 4A elements and oxygen.
Textbook Question
Sodium hydride, NaH, crystallizes in a face-centered cubic unit cell similar to that of NaCl (Figure 12.11). How many Na+ ions touch each H- ion, and how many H- ions touch each Na+ ion?
Textbook Question
Iron crystallizes in a body-centered cubic unit cell with an edge length of 287 pm. Iron metal has a density of 7.86 g>cm3 and a molar mass of 55.85 g. Calculate a value for Avogadro's number.