# Problem: At room temperature and pressure RbI crystallizes with the NaCl-type structure.At high pressure the structure transforms to one with a CsCl-type structure. Use ionic radii to predict the length of the cubic unit cell edge for the high-pressure form of RbI. Radius of Rb+ is 1.52 Å and I- is 2.20 Å

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###### FREE Expert Solution
• At conditions of high pressure, RbI will appear to have a similar structure like CsCl.
• CsCl is known to have a body centered cubic structure
• Ionic radius of rubidium and iodide ions are 1.52 Å and 2.20 Å
• Body diagonal of a BCC structure is composed of 4 radii of the atoms (2 radii of each ion)
• Based on the Pythagorean theorem, edge length can be calculated using the formula: ###### Problem Details

At room temperature and pressure RbI crystallizes with the NaCl-type structure.

At high pressure the structure transforms to one with a CsCl-type structure. Use ionic radii to predict the length of the cubic unit cell edge for the high-pressure form of RbI. Radius of Rbis 1.52 Å and Iis 2.20 Å