Silver is a soft, lustrous transition metal with the highest electrical and thermal conductivity of all metals. It is used in electronics, photography, jewelry, and mirrors, and tarnishes in the presence of sulfur compounds.
Silver has the ground-state configuration [Kr] 4d10 5s1, often described as "anomalous" relative to a naive Aufbau prediction of 4d95s2. A filled 4d subshell plus a single 5s electron lowers the total energy via exchange and subshell stability.
At room temperature, conduction is dominated by a single, nearly-free 5s electron per Ag atom with minimal scattering from lattice imperfections. Its wide, half-filled s-band provides a high carrier density and mobility, yielding exceptional electrical and thermal conductivity (linked by the Wiedemann–Franz law).
Silver most commonly exhibits +1 (Ag+), while +2 and +3 occur in specialized complexes or oxidizing conditions. Useful species include:
Silver tarnishes due to reaction with sulfur compounds in air (e.g., H2S), forming black silver sulfide on the surface.
\(\mathrm{2\,Ag(s) + H_2S(g) \rightarrow Ag_2S(s) + H_2(g)}\)
Polishing or chemical dips convert \(\mathrm{Ag_2S}\) back to metallic Ag or remove the film.
Although AgCl is sparingly soluble, ammonia or thiosulfate ligands form stable complexes with Ag+, shifting equilibria and dissolving precipitates:
\(\mathrm{AgCl(s) + 2\,NH_3(aq) \rightleftharpoons [Ag(NH_3)_2]^+(aq) + Cl^-(aq)}\)
\(\mathrm{AgBr(s) + 2\,S_2O_3^{2-}(aq) \rightleftharpoons [Ag(S_2O_3)_2]^{3-}(aq) + Br^-(aq)}\)
Light causes photochemical reduction of silver halides (AgBr, AgCl) to metallic silver specks that seed image formation. A simplified step is:
\(\mathrm{AgBr(s) + h\nu \rightarrow Ag(s) + Br^{\bullet}}\)
Development amplifies these specks to a visible metallic silver image; fixing removes unexposed halide.
Tollens’ reagent, \(\mathrm{[Ag(NH_3)_2]^+}\), oxidizes aldehydes to carboxylates while reducing Ag(I) to metallic silver that deposits as a mirror on glass:
\(\mathrm{R{-}CHO + 2\,[Ag(NH_3)_2]^+ + 3\,OH^- \rightarrow R{-}COO^- + 2\,Ag(s) + 4\,NH_3 + 2\,H_2O}\)
Sterling silver is an alloy containing 92.5% Ag and 7.5% Cu. Copper increases hardness and wear resistance while maintaining luster and workability—ideal for jewelry and flatware.
Yes. Ag+ ions disrupt microbial cell membranes and enzyme systems. This underlies uses in wound dressings, coatings, and water disinfection. Safety-wise, controlled doses and immobilized forms are preferred to minimize environmental release.
Silver’s high reflectivity across the visible spectrum makes it excellent for mirrors and optical components. Protective overcoats (e.g., SiO2, Al2O3) are often added to reduce tarnishing while preserving reflectance.