What metallic element in radiograph film turns black upon exposure and processing?

The metallic element in radiograph film that turns black upon exposure and processing is silver. Radiographic films are coated with a layer of silver halide crystals, primarily silver bromide. When the film is exposed to radiation, these silver halide crystals undergo a photochemical reaction; the areas that receive radiation result in the reduction of silver halides to metallic silver.

During the development process, these metallic silver particles form the dark areas visible on the radiograph. The more radiation exposure a particular area of the film receives, the more silver is deposited, resulting in darker regions on the film. This characteristic makes silver a fundamental component in traditional radiographic imaging, as it allows for the contrast needed to visualize different structures within the body. The chemistry involved is critical in understanding how radiographs are produced and interpreted in clinical practice.