A Window on the Solid State: Part I: Structures of Metals; Part II: Unit Cells of Metals; Part III: Structures of Ionic Solids; Part IV: Unit Cells of Ionic Solids
William R. Robinson and Joan F. Tejchma Department of Chemistry, Purdue University, West Lafayette, IN 47907-1393
Note:	This program is included in both the General Chemistry Collection (SP-16) and the Advanced Chemistry Collection (SP-28). To Order General Chemistry Collection To Order Advanced Chemistry Collection
A Window on the Solid State helps students understand and instructors present the structural features of solids. Parts I and II were published previously by JCE Software (1) and Macintosh versions of Parts I and II are also available (2). Parts I and II have been updated to include improvements in art and minor changes in logic. Parts III and IV expand the collection to include the structures of simple ionic solids using the visual effects available in an interactive computer medium. The package provides a tour of the structures commonly used to introduce features of the solid state. Screens from Parts III and IV of A Window on the Solid State Part I: Structures of Metals introduces the four basic structural types found in metals: the hexagonal closest-packed structure, the cubic closest-packed structure, the body-centered cubic structure, and the simple cubic structure. These structures are introduced as stacks of close-packed planes of metal atoms in the hexagonal- and cubic-closest packed structures, and stacks of less efficiently packed planes in the other two structures. In addition, Part I also introduces Laves's principle, coordination number, stacking of planes, efficiency of packing, and how to draw the structures using two-dimensional representations. The pseudo-animation used is particularly effective in distinguishing between hexagonal close-packing and cubic close-packing. Part II: Unit Cells of Metals addresses the use of a unit cell to describe a two-dimensional structure, then extends the concept to describing the structures of metals using the four basic unit cells of the metals: the simple cubic, body-centered cubic, face-centered cubic, and hexagonal cells. The relationships between the radii of metal atoms in the cubic structures and the cell dimensions are developed. Students are also introduced to counting the number of atoms in a unit cell. Pseudo-animation is particularly effective in illustrating the fractions of atoms that lie in the various unit cells. Part III: Structures of Ionic Solids describes simple ionic structures in terms of the packing of positive ions in holes in arrays of negative ions. In the course of the presentation, the features common to the packing of ions in binary ionic solids are described. Animation is used to introduce the radius ratio rule (smaller ions ÒrattleÓ in larger holes and larger ions do not fit into smaller holes). Tetrahedral and octahedral holes are highlighted in closest packed arrays of anions. Then the coordinating anions are isolated and rotated to show their geometry. Cubic holes appear in simple cubic arrays of anions. Finally, the CsCl, CaF2, NaCl, TiO2, and cubic ZnS structures are built layer by layer using animation to show alternating layers of anions and cations and discuss the type and fraction of holes occupied. Part IV: Unit Cells of Ionic Solids discusses the unit cells of five common ionic structures: the CsCl, CaF2, NaCl, TiO2, and cubic ZnS structures. A pseudo-animation is particularly effective in illustrating the relation of the unit cell to the extended structures described in Part III. The locations of ions of each cell are illustrated with space-filling and ball-and-stick models. When appropriate, the relationship of alternate unit cells is described. Coordination numbers of cations and anions are highlighted and students are shown how to determine the numbers of ions in a unit cell. Pseudo-animation is particularly effective in illustrating the fractions of atoms that lie in the various unit cells. The relationships between the ionic radii and cell dimensions are developed. All four parts of A Window on the Solid State can be used by students in individual or group tutorial settings. Students can work through the material at their own pace. Each part requires students to identify or predict structural features and includes pop-up boxes that confirm or correct choices. Hotwords are used to link ideas and provide definitions. Parts I and II also have versions optimized for classroom presentation. Hardware and Software Requirements   Computer  CPU RAM Drives Graphics Free Disk Space System Software Other   Solid State Structures Windows compatible  80386 or higher with math coprocessor 8 MB  Hard disk, 3.5-in. high-density floppy drive 640 x480, 256 colors 2 MB  Windows 3.11 with Win32s or Windows 95  PCMolecule2 or PCMolecule2 Lite   A Window on the Solid State Windows compatible  80386 or higher or Pentium 8 MB  Hard disk, 3.5-in. high-density floppy drive 640 x480, 256 colors  14 MB  Windows 3.1x or Windows 95 --  Acknowledgement Parts I and II of this program were written while the author was on sabbatical as a 1992-93 SERAPHIM Fellow at The University of WisconsinÐMadison. The support of Purdue University and the National Science Foundation through grant #MDR-9154099 is gratefully appreciated. Literature Cited Robinson, W. R. A Window on the Solid State; J. Chem. Educ. Software 1994, 2D No. 2. Robinson, W. R.; Sari, C. P. A Window on the Solid State for Macintosh; J. Chem. Educ. Software 1994, 6C No. 2.

First Published: September 1997

Citation: Robinson, W. R.; Tejchma, J. F. . A Window on the Solid State: Part I: Structures of Metals; Part II: Unit Cells of Metals; Part III: Structures of Ionic Solids; Part IV: Unit Cells of Ionic Solids J. Chem. Educ. Software 5D2

Keywords: Lecture Aid; Computer Room; High School; General; Inorganic; Solid state

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Last Updated: July 19, 2001 Created: November 13, 1997	Created by: N. S. Gettys Comments to: jceonline@chem.wisc.edu
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