• coordination # increases with issue: how many anions can you arrange around a cation?
DESCRIPTION
COORDINATION # AND IONIC RADII. • Coordination # increases with Issue: How many anions can you arrange around a cation?. Adapted from Fig. 12.4, Callister 6e. Adapted from Fig. 12.2, Callister 6e. Adapted from Fig. 12.3, Callister 6e. Adapted from Table 12.2, Callister 6e. - PowerPoint PPT PresentationTRANSCRIPT
• Coordination # increases with Issue: How many anions can you arrange around a cation?
rcationranion
rcationranion
Coord #
< .155 .155-.225 .225-.414 .414-.732 .732-1.0
ZnS (zincblende)
NaCl (sodium chloride)
CsCl (cesium chloride)
2 3 4 6 8
Adapted from Table 12.2, Callister 6e.
Adapted from Fig. 12.2, Callister 6e.
Adapted from Fig. 12.3, Callister 6e.
Adapted from Fig. 12.4, Callister 6e.
COORDINATION # AND IONIC RADII
• On the basis of ionic radii, what crystal structure would you predict for FeO?
• What are the lattice parameter, the density and the packing factor? Cation
Al3+
Fe2+
Fe3+
Ca2+ Anion
O2-
Cl-
F-
Ionic radius (nm)
0.053
0.077
0.069
0.100
0.140
0.181
0.133
• Answer:
rcationranion
0.0770.140
0.550
based on this ratio,--coord # = 6--structure = NaCl
Data from Table 12.3, Callister 6e.
EXAMPLE: PREDICTING THE STRUCTURE OF FeO
a = 2(0.077) + 2(0.14) = 0.434 nm
= {(4x55.85) + (4x16)}/{(0.434x10-7 cm)3 (6.02x1023 atoms/mol)} = 5.84 g/cm3
P.F. = {(4/3)(4 ions/cell)(0.0773 + 0.143)}/(0.434)3 = 0.656