Answer:
Silver tarnishes over time due to a chemical reaction with sulfur compounds in the environment. The tarnishing process involves the following steps:
Exposure to Sulfur Compounds: Silver items come into contact with sulfur compounds found in the air, as well as in materials like rubber, wool, and certain foods. Hydrogen sulfide (H2S) and sulfur dioxide (SO2) are common sources of sulfur.
Formation of Silver Sulfide: When silver reacts with sulfur compounds, it forms silver sulfide (Ag2S). This reaction can be represented as follows:
4Ag + 2H2S + O2 -> 2Ag2S + 2H2O
Silver sulfide is a dark compound that gives silver items a black or gray tarnish.
Surface Discoloration: As silver sulfide accumulates on the surface of the silver item, it creates a dark, tarnished layer. This layer can be unsightly and diminish the luster of the silver.