Final answer:
The radius of a cesium atom in a body-centered cubic system with an edge length of 612 pm is 265 pm. The correct answer is option A.
Step-by-step explanation:
Cesium crystallizes in the body-centered cubic system, where the cesium atoms are located at the corners of the unit cell and at the center of the cell. In a body-centered cubic structure, the edge length is equal to 4 times the body diagonal of the unit cell. Therefore, the body diagonal length of the unit cell is 612 pm / sqrt(3).
The radius of a cesium atom can be calculated using the formula r = a / (4 * sqrt(3)), where r is the atomic radius and a is the edge length of the unit cell. Substituting the given values, we get r = 612 pm / (4 * sqrt(3)) = 265 pm. Therefore, the radius of a cesium atom is 265 picometers (pm).