Unit cell of sodium chloride

The contents of the unit cell of any compound must contain an integral number of formula units. (Why ) Note that unit cell boundaries slice" atoms into fragments An atom on a face Will be split in half between two cells one on an edge will be splu into gunners among Jour cells, etc Identify the number of Na and Cl ions in the unit cell of sodium chloride illustrated in Fig. 4.1a and state how many formula units of NaCl the unit cell contains. Give a complete analysis. 

Fig. 4.1 Crystal structures of two 1 1 ionic compounds (a) unit cell of sodium chloride, cubic, space group Fm3m (b) unit cell of cesium chloride, cubic, space group Fm3m. [From Ladd, M.F C Structure and Bonding in Solid State Chemistry, Wiley New York, 1979. Reproduced with permission.]...

Millions of unit cells make up a crystal. The larger a molecule the smaller the number of unit cells found in a fixed crystal volume. The unit cell of sodium chloride is a cube, a = 5.6 A in each direction there are approximately 10 unit cells- in a crystal 1 mm on an edge (volume IQSi enzyme D-xylose isomerase crystallizes with a unit cell... 

Figure 13-28 Some representations of the crystal structure of sodium chloride, NaCl. Sodium ions are shown in gray and chloride ions are shown in green, (a) One unit cell of the crystal strucmre of sodium chloride, (b) A representation of the unit cell of sodium chloride that indicates the relative sizes of the Na and Cl ions as well as how ions are shared between unit cells. Particles at the corners, edges, and faces of unit cells are shared by other unit cells. Remember that there is an additional Na ion at the center of the cube, (c) A cross-section of the strucmre of NaCl, showing the repeating pattern of its unit cell at the right.

In certain types of solids, including ionic crystals, particles different from those at the corners of the unit cell occupy extra positions within the unit cell. For example, the face-centered cubic unit cell of sodium chloride can be visualized as having chloride ions at the corners and middles of the faces sodium ions are on the edges between the chloride ions and in the center (see Figure 13-28). Thus, a unit cell of NaCl contains the following. 

Figure 11.42 shows the unit cell of sodium chloride. It has Cl ions at the corners as well as at the center of each cube face. Because the chloride ions are so much larger than the sodium ions, the CP ions are nearly touching and form an approximate cubic close-packed stracture of CP ions. The Na" ions are arranged in cavities of this close-packed structure. Some other compounds that crystallize in this stracture are potassium chloride, KCl calcium oxide, CaO and silver chloride, AgCl. 

Fig. 9.7. Compound lattices and unit cells of sodium chloride and cesium chloride.

Show that the structure of the unit cell for sodium chloride (Figure 5.15b) is consistent with the formula NaO. 

Sketch/describe unit cells for sodium chloride, cesium chloride, zinc blende, diamond cubic, fluorite, and perovskite crystal structures. Do likewise for the atomic structures of graphite and a silica glass. 

The rocksalt stmcture is illustrated in figure Al.3.5. This stmcture represents one of the simplest compound stmctures. Numerous ionic crystals fonn in the rocksalt stmcture, such as sodium chloride (NaCl). The conventional unit cell of the rocksalt stmcture is cubic. There are eight atoms in the conventional cell. For the primitive unit cell, the lattice vectors are the same as FCC. The basis consists of two atoms one at the origin and one displaced by one-half the body diagonal of the conventional cell. 

Electrolytic Preparation of Chlorine and Caustic Soda. The preparation of chlorine [7782-50-5] and caustic soda [1310-73-2] is an important use for mercury metal. Since 1989, chlor—alkali production has been responsible for the largest use for mercury in the United States. In this process, mercury is used as a flowing cathode in an electrolytic cell into which a sodium chloride [7647-14-5] solution (brine) is introduced. This brine is then subjected to an electric current, and the aqueous solution of sodium chloride flows between the anode and the mercury, releasing chlorine gas at the anode. The sodium ions form an amalgam with the mercury cathode. Water is added to the amalgam to remove the sodium [7440-23-5] forming hydrogen [1333-74-0] and sodium hydroxide and relatively pure mercury metal, which is recycled into the cell (see Alkali and chlorine products). 

Potassium iodide has a unit cell similar to that of sodium chloride (Figure 9.18). The ionic radii of K+ and I- are 0.133 nm and 0.216 nm, respectively. How long is... 

FIGURE 5.40 Bill ions of unit cells stack together to recreate the smooth faces of the crystal of sodium chloride seen in this micrograph. The first inset shows some of... 

Assume that the iron atoms in the crystal are in a perfect array, identical to the metal atoms in the sodium chloride structure, and that the 0.058 excess of oxygen is due to interstitial oxygen atoms being present, over and above those on the normal anion positions. The unit cell of the structure now contains 4 Fe and (4 x 1.058) O. The density is calculated to be 6076 kg m-3. 

Figure 1.14 Crystal structure of sodium chloride, NaCl (a) a perspective view of one unit cell and (h) projection down [010], the b axis.

Pure potassium bromide, KBr, which adopts the sodium chloride structure, has the fraction of empty cation sites due to Schottky defects, ncv/Nc, equal to 9.159xl0-21 at 20°C. (a) Estimate the enthalpy of formation of a Schottky defect, Ahs. (b) Calculate the number of anion vacancies per cubic meter of KBr at 730°C (just below the melting point of KBr). The unit cell of KBr is cubic with edge length a = 0.6600 nm and contains four formula units of KBr. 

In general, any ionic solid can be pictured as a unit cell in which the cations are surrounded by a number of anions and the anions are surrounded by a number of cations. A typical example is that of sodium chloride (Fig. 6.1). 

An alternative way of viewing this structure is to think of it as a cubic close-packed array of chloride Ions with sodium Ions filling all the octahedral holes. The conventional unit cell of a ccp array Is an F face-centred cube (hence the cubic in ccp) the close-packed layers lie at right angles to a cube diagonal (Figure 1.32). Filling all the... 

If you have a class with biochemists, clearly the area of enzyme kinetics is practically mandatory. If biologists are mixed in with the biochemists, osmotic pressure is an important concept to cover carefully and a concept typically not well covered in general chemistry and in most physical chemistry texts or classes. A quick example what is a 2 Osmolar solution of sodium chloride Such concentration units are used when dispensing various saline solutions in hospitals. What is the origin of the unit A 1 M NaCl solution dissociates into two ions that would double the osmotic pressure of a non dissociating solute. Thus, the 1 M solution of NaCl becomes a 2 Osmolar solution. Other examples abound - the bursting pressure of a cell relates to the osmotic pressure of the serum in which the cell finds itself. 

FIGURE 10.24 The unit cell of NaCl in both (a) a skeletal view and (b) a space-filling view in which one face of the unit cell is viewed head-on. The larger chloride anions adopt a face-centered cubic unit cell, with the smaller sodium cations fitting into the holes between adjacent anions. 

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