Silver

 

Silver is a metallic element and the most reactive of the noble metals, which also includes platinum.

Conventional photography is based on the sensitivity of silver halides — binary compounds — to light. A black and white photographic image is comprised of microscopic particles of metallic silver suspended in a gelatin emulsion.

https://www.nfsa.gov.au/sites/default/files/uploads/2010/08/25/silver.jpg

 

In its metallic form silver is relatively stable, but it is readily oxidised or attacked by sulfur compounds.