Chapter 9 Structural chemistry of ionic compounds 9.1 The ionic radii ratio and the coordination polyhedra of ions Interstices octahedral holes tetrahedral holes hole size is 0.414R hole size is 0.225R CN:6 CN:4
Chapter 9 Structural chemistry of ionic compounds 9.1 The ionic radii ratio and the coordination polyhedra of ions octahedral holes hole size is 0.414R CN: 6 tetrahedral holes hole size is 0.225R CN: 4 Interstices
Interstice type C.N. Thole/R Triangular 3 0.155 Tetrahedal 4 0.225 Octahedral 6 0.414 Cubic 8 0.732 Cuboctahedron 12 1.000 The rule of the packing of ions 88
Triangular 3 0.155 Tetrahedal 4 0.225 Octahedral 6 0.414 Cubic 8 0.732 Cuboctahedron 12 1.000 Interstice type C.N. rhole /R The rule of the packing of ions
Table 1.The limiting ratio of some coorrdination Coordination polyhedra C.N minimum r,/r. Triangular 3 0.155 Tetrahedal 4 0.225 Octahedral 6 0.414 Cubic 8 0.732 Cuboctahedron 12 1.000 9.2 The crystal structures of Some typical ionic compounds Answer the following questions: The packing style of anions The position of cations Crystal System (Bravais Lattice)? The C.N.of anion and cation Atom number in one unit cell? ·Structural formula? ·Atomic coordinates
Coordination polyhedra C.N. minimum r+/rTriangular 3 0.155 Tetrahedal 4 0.225 Octahedral 6 0.414 Cubic 8 0.732 Cuboctahedron 12 1.000 Table 1. The limiting ratio of some coorrdination 9.2 The crystal structures of Some typical ionic compounds Answer the following questions: • The packing style of anions ? • The position of cations ? • Crystal System (Bravais Lattice)? • The C.N. of anion and cation ? • Atom number in one unit cell? • Structural formula ? • Atomic coordinates
ZnS (0.225-0.414) CN+CN.-4:4 (Sphalerite) ·The packing of fec anions .Bravais Lattice Cubic F •The position of V2 Tetrahedral cations: holes Zn:S =4:4 cubic The C.N.of cation 4:4 and anion: A:0,0,0,1/2,1/2,0,1/2,0,1/2 0,1/2,1/2 ·Atom number in 4:4 B:3/4,1/4,1/4:1/4,3/4,1/4: one unit cell: 1/4,1/4,3/4;3/4,3/4,3/4 ZnS (0.225-0.414 (Wurtzite) ·The packing of hcp anions: .Bravais Lattice Hexagonal P .The position of 2 Tetrahedral cations: holes The C.N.of cation 4:4 and anion: Zn:S 2:2 hexagonal ·Atom number in 2:2 A:0,0,0,1/3,2/3,1/2 one unit cell: B:0,0,3/8,1/3,2/3,7/8 CuF,CuCl,CuBr,Cul;AgI;ZnO,ZnS,ZnSe,ZnTe;CdO,CdS, CdSe,CdTe;HgS,HgSe,HgTe
ZnS (0.225-0.414) C.N.+:C.N.- 4:4 (Sphalerite) Zn:S = 4:4 cubic A: 0,0,0; 1/2,1/2,0, 1/2,0,1/2; 0,1/2,1/2 B: 3/4,1/4,1/4; 1/4,3/4,1/4; 1/4,1/4,3/4; 3/4,3/4,3/4 •Bravais Lattice : Cubic F • Atom number in 4:4 one unit cell: The C.N. of cation 4:4 and anion: ½ Tetrahedral holes •The position of cations: • The packing of fcc anions: Zn:S = 2:2 hexagonal A: 0,0,0, 1/3,2/3,1/2 B: 0,0,3/8; 1/3,2/3,7/8 (Wurtzite) ZnS (0.225-0.414) CuF, CuCl, CuBr, CuI; AgI; ZnO, ZnS, ZnSe, ZnTe; CdO, CdS, CdSe, CdTe; HgS, HgSe, HgTe •Bravais Lattice : Hexagonal P • Atom number in 2:2 one unit cell: The C.N. of cation 4:4 and anion: ½ Tetrahedral holes •The position of cations: • The packing of hcp anions:
NaCl(0.732-0.414)Cubic,.C.N+c.N-66, ·The packing of fec anions .Bravais Lattice Cubic F .The position of Octahedral cations: holes The C.N.of 6:6 Na:Cl 4:4 cation and anion: A:0,0,0;1/2,1/2,0,1/2,0,1/2,0,1/2,1/2 ·Atom number 4:4 B:1/2,1/2,1/2;1/2,0,0:0,1/2,0,0,0,1/2 in one unit cell: (0.732-0.414)KCl,KBr,SrS,RbI,BaTe,SrSe,CaS,KI,SrTe,MgO, LiF,CaSe,NaBr,CaTe,MgS,NaI,LiCl,(>0.732)KF,SrO,BaO, RbF,RbCl,BaS,CuO,CsF,RbBr,BaSe,NaF,(<0.414)MgSe, LiBr,LiF NiAs(0.732-0.414) Hexagonal,C.N.+:C.N.6:6, (0.732-0.414)FeS
NaCl (0.732-0.414) Cubic, C.N.+:C.N.- 6:6, Na:Cl = 4:4 A: 0,0,0; 1/2,1/2,0, 1/2,0,1/2; 0,1/2,1/2 B: 1/2,1/2,1/2; 1/2,0,0; 0,1/2,0, 0,0,1/2 (0.732-0.414) KCl, KBr, SrS, RbI, BaTe, SrSe, CaS, KI, SrTe, MgO, LiF, CaSe, NaBr, CaTe, MgS, NaI, LiCl, (>0.732) KF, SrO, BaO, RbF, RbCl, BaS, CuO, CsF, RbBr, BaSe, NaF, (<0.414) MgSe, LiBr, LiF •Bravais Lattice : Cubic F • Atom number 4:4 in one unit cell: The C.N. of 6:6 cation and anion: Octahedral holes •The position of cations: • The packing of fcc anions: NiAs (0.732-0.414) Hexagonal, C.N.+:C.N.- 6:6, (0.732-0.414) FeS