Silver

About Silver

Silver has the highest electrical and thermal conductivity of any element — 6.3 × 10⁷ S/m at room temperature, just edging out copper — and the highest visible-light reflectance of any metal at over 95%. The Latin 'argentum' lives on in the symbol Ag and in country names (Argentina). Chemically it is dominated by Ag(I): a soft Lewis acid that loves S, P, and halide ligands, and forms the famously light-sensitive silver halides AgCl, AgBr, and AgI. That photochemistry built an entire industry — silver halide grains in gelatin emulsion are still how analog film captures light, and the same chemistry produces the photochromic darkening in transition lenses. In coordination chemistry, [Ag(NH₃)₂]⁺ — Tollens' reagent — is what undergrad organic students use to spot aldehydes via the silver-mirror test. Antimicrobially, Ag⁺ disrupts bacterial respiratory enzymes and membrane integrity at sub-micromolar concentrations, which is why silver sulfadiazine cream sits on burn wards and silver-impregnated catheters reduce nosocomial infections. The metal's tarnish is Ag₂S, formed by reaction with trace H₂S in air — annoying for cutlery, terminal for old photographs.