Silver (chemical symbol Ag, atomic number 47) is a silver-white transition metal. In nature, a small amount exists in the form of free simple substance (mainly in ores containing silver compounds).

Silver has stable chemical properties, low activity, good thermal and electrical conductivity, is not easy to be corroded by chemical substances (except silver nitrate, sulfur and hydrogen sulfide), and can react with oxygen at high temperature to generate silver oxide, which is soft and malleable.

So silver is not afraid of water, silver nitrate, sulfur and hydrogen sulfide. Fear of high temperature and lack of oxygen, followed by impure air. Pure oxygen is not afraid at room temperature, because the air contains about 0.0 1mg/L of hydrogen sulfide, and the principle that silver is easy to turn yellow and black in the air is like this. The reaction formula is written as 4Ag+2H2S+O2=2Ag2S+2H2O.