All silver, plate, fill, sterling and fine tarnishes when its alloy metal, copper, is exposed to chlorides and sulfurs in the air. Argentium sterling silver is the most tarnish resistant because it contains more pure silver and the metalloid germanium replaces some of the copper used as an alloy in it.
Properly clean and store silver to prevent it from oxidizing. Wash dirty silver with water and a mild dish soap that doesn't contain lemon. Gently buff sterling silver using a clean, lint-free, soft cotton cloth. Store silver in a sealed polyethylene plastic bag to minimize and prevent tarnishing between uses.