Identify the structure of each of the two unit cells shown in Problem 52 as the rock salt structure, zinc blende structure, fluorite structure, antifluorite structure, or none of these.

Verified step by step guidance

1. Identify the characteristics of each structure: Rock salt structure is based on a face-centered cubic (FCC) lattice with each ion type occupying octahedral sites. Zinc blende structure is also based on an FCC lattice but with one ion type occupying tetrahedral sites. Fluorite structure has a cubic arrangement where cations are in a face-centered cubic lattice and anions occupy all tetrahedral sites. Antifluorite structure is the inverse of fluorite, with anions in the FCC lattice and cations in tetrahedral sites.
2. Examine the coordination number and arrangement of ions in each unit cell: Determine the coordination number of each ion type in the unit cells provided. Rock salt has a coordination number of 6:6, zinc blende has 4:4, fluorite has 8:4, and antifluorite has 4:8.
3. Compare the unit cell's ion arrangement to known structures: Check if the arrangement of ions in the unit cells matches any of the known structures based on their coordination numbers and lattice types.
4. Determine if the unit cells match any of the given structures: If the arrangement and coordination numbers match one of the known structures, identify it as such. If not, classify it as 'none of these'.
5. Conclude the identification process: Based on the analysis, assign the correct structure to each unit cell or determine that it does not match any of the specified structures.

Key Concepts

Unit Cell

A unit cell is the smallest repeating unit in a crystal lattice that reflects the symmetry and structure of the entire crystal. It defines the arrangement of atoms, ions, or molecules in three-dimensional space. Understanding unit cells is crucial for identifying the overall structure of a crystalline material, as they determine the properties and behavior of the solid.

Crystal Structures

Crystal structures refer to the organized arrangement of atoms within a crystalline solid. Common types include rock salt (NaCl), zinc blende (ZnS), fluorite (CaF2), and antifluorite (Li2O). Each structure has distinct coordination numbers and geometries, which influence the material's physical and chemical properties, making it essential to recognize these patterns for classification.

Coordination Number

The coordination number is the number of nearest neighbor atoms or ions surrounding a central atom in a crystal structure. It plays a significant role in determining the stability and geometry of the crystal. For example, in the rock salt structure, the coordination number is 6, indicating that each ion is surrounded by six oppositely charged ions, which is key to understanding the properties of ionic compounds.