A silver article generally turns black when kept in the open for a few days. The articles when rubbed with toothpaste again starts shining. (i) Why do they turn black ? Name the phonomenon involved. (ii) Name the black substance formed and write its formula.

A silver article generally turns black when kept in the open for a few

1.	A silver article generally turns black when kept in the open for a few days. The articles when rubbed with toothpaste again starts shining. (i) Why do they turn black ? Name the phonomenon involved. (ii) Name the black substance formed and write its formula.
Answer» Solution :(i) Silverarticle reacts with SULPHUR compounds such as `H_(2)S` PRESENT in air . The phenomenon is CALLED corrosion. For silver PARTICULARLY, it is called tranishing of silver. (ii) The black substance is islver sulphide `(Ag_(2)S)`.