NaCI lattice

Fig. 16.5 Partial structure of CU-9 showing a polyhedral Cu-O-P chain that wraps around the salt lattice, see text. The former is constructed by sharing corner oxygen atoms of alternating square planar CUO4 and tetrahedral P2O7 units. The salt lattice adopts the NaCI core in which each cubical unit is made of 1 /8 of the unit cell structure of the NaCI lattice. Alternating cubical units are highlighted for clarity.

In the case of an f.c.c. AI structure, with u = w = 1, the state of complete occupation of interstitial carbon corresponds to a MC carbide with the NaCI lattice. For the c.p.h. A3 structure, with = 1 and v = 0.5, complete occupation of the interstitial sites by carbon gives the MjC carbide with a hexagonal Fe2N-type structure. 

Lithium iodide crystallizes in the NaCI lattice despite the fact that r+/r is less than 0.414. Its density is 3.49g/cm Calculate from these data the ionic radius of the iodide ion. 

By assuming an electrostatic model, estimate the lattice energy of MgO (NaCI lattice) values of rj are listed in Appendix 6. /4 v. —3926 kJ mol ... 

Cubic crystals (NaCI lattice) or white fluffy powder, d9 2.640. mp 848° hp 1681. Volatilizes at 1100-1200 Soly in water (25 ) 0.13 g/100 ml. Soluble in acids. With hydrofluoric acid it forms lithium bifluoride, LiHF2. With lithium hydroxide it forms a double salt LiF.LiOH, mp 462. LD orally in guinea pigs 200 mg/kg. 

Cubic crystals (NaCI lattice). Usually obtained as white, deliquesc powder or solid. Poisonous d 2.481. mp 859.9". bp 1505. Soly in water g/100 ml) 92.3 (18 ) 96.4 (21°). Very freely sol in boiling water. Also sol in aq HF, liq NH. Insol in alcohol unless water is present. May be stored in aluminum containers. Coution Attracts moisture from the air. Aq solns corrode glass and porcelain. MLD orally in guinea pigs 250 mg/kg,... 

Hard, shiny, crystals which deliquesce when breathed upon, but which resolidify immediately in dry air. Not hygroscopic in the usual sense. Orthorhombic (deformed NaCI lattice), dj 8.36. mp 322°. Bagins to sublime at 300°. Very freely sol in water. Coned solns show strong alkalinity. 

NaCI lattice. [Reproduced from http //en.wikipedia.org/wiki/Sodium chloride (accessed January I I, 2014).]... 

Using the crystal radii listed in Table 5.2 and assuming that the ions just touch along an edge in the NaCI lattice pictured below, calculate the density of NaCI in units of gfcmT... 

Use data from Table 5.2 to determine whether Rbl will crystallize in the NaCI lattice or CsCI lattice. Then use the appropriate Madelung constant and compressibility factor In the Born-Lande equation to calculate the lattice energy. Given that the sublimation enthalpy of Rb is 82 kJ/mol and its first ionization energy is 403 kJ/mol, the bond... 

Tin(II) sulphide may be made by the direct combination of the elements, but this product is usually non-stoichiometric it is usually obtained by the sulphide precipitation of tin(II) salts, whence the initially hydrated form is easily dehydrated. Crystalline SnS, m.p. 1153°K, b.p. 1500°K, density 5, has a very distorted NaCl structurei o in which each tin atom has four different near neighbour sulphur distances of 2-62A, 2-68 A (2), 3 27 A (2) and 3-39 A. The analogous PbSnS2 which occurs in Bolivian ores as the mineral theallite has the same distorted structure, in marked contrast to the perfect NaCI lattice of PbS. 

FIGURE 1 4 An ionic bond IS the force of attrac tion between oppositely charged ions Each Na ion (yellow) in the crystal lattice of solid NaCI IS involved in ionic bonding to each of six surrounding Cl ions (green) and vice versa... 

Figure 6.9 B12 Cubo-octahedral cluster as found in MBj2. This Bj2 cluster alternates with M atoms on an fee lattice as in NaCI, the Bj2 cluster replacing Cl.

It is convenient to draw micro-twin structures derived from the micro-twinning of a CCP lattice projected on the normal plane to the pillars of the trigonal prisms. Let us consider a twin structure derived from a NaCl-type structure, in which both anions and cations have a CCP arrangement. Figure 2.67 shows the structure of a NaCl-type (a) is projected on (OOl)Naci and (b) on (110). It can be easily shown that the twin plane (203) ,j in the ortho-hexagonal expression corresponds to the (113) plane in the cubic one. Figure 2.68 shows a twin structure of NaCl-type,... 

The enthalpy of formation of an ionic compound can be calculated with an accuracy of a few percent by means of the Born-Land6 equation (Eq. 4.13) and the Bcrn-Haber cycle. Consider NaCI. for example. We have seen that by using the predicted internuclear distance of 283 pm (or the experimental value of 281.4 pm), the Madelung constant of 1.748, the Rorn exponent, n, and various constants, a value of — 755 kJ mol-1 could be calculated for the lattice energy. The heat capacity correction is 2.1 kJ mol-1, which yields U 9i = —757 kJ mol-1. The Bom-Haber summation is then... 

Anions and cations pack together into a crystal lattice as shown to the right for NaCI. Ionic compounds are also known as salts. 

A. Heat is required to break bonds in the NaCI crystal lattice. 

In solid sodium chloride, NaCI, sodium and chlorine are arranged in a rigid lattice pattern. 

The cesium ion is larger than the sodium ion so it s possible for eight chloride ions to fit around a single cesium ion in the CsCI crystal lattice. The smaller sodium Ion can accommodate only six chloride Ions In the NaCI structure. 

---