2. CERAMIC BONDING • Bonding: --Mostly ionic, some covalent. --% ionic character increases with difference in electronegativity. Adapted from Fig. 2.7, Callister 6e. (Fig. 2.7 is adapted from Linus Pauling, The Nature of the Chemical Bond , 3rd edition, Copyright 1939 and 1940, 3rd edition. Copyright 1960 by Cornell University. • Large vs small ionic bond character:

3. Rules for Ionic Structures • Rule 1: Charge Neutrality : --Net charge in the structure should be zero. --General form:

6. COORDINATION # AND IONIC RADII • Coordination # increases with: Issue: How many anions can you arrange around a cation? Adapted from Table 12.2, Callister 6e. There are many possibilities—how do we generally determine which is appropriate? And what do we call them? Binary Trigonal Tetrahedral Octahedral Cubic

10. Which crystal structures are appropriate?

18. A m X p STRUCTURES • Consider CaF 2 : • Based on this ratio, coord # = 8 and structure = CsCl. • BUT: there are half as many Ca 2+ as F - ions—how can we accommodate this? CsCl structure w/only half of cation sites occupied. Adapted from Fig. 12.5, Callister 6e. m is not equal to p

19. Silicon oxides Building Block: SiO 4 4-

20. Quartz, SiO 2 Hexagonal - Trigonal trapezohedral

21. SiO x There are three polymorphs of SiO 2 : Quartz, Cristobalite, and Tridymite

23. Glasses Can we form glass structures in metals? YES, you need to cool them very fast, 10 6o C/sec…

24. Glass Production

25. Carbon

26. Crystals often indicate crystal structure