Metallic calcium was prepared by British chemist David and Swedish chemist Berzilius in 1809. Calcium is a silver white metal, harder and heavier than lithium, sodium, and potassium; Melt at 815 ℃. The chemical properties of metallic calcium are very active. In the air, calcium is quickly oxidized and covered with an oxide film. When heated, calcium will burn and emit a beautiful brick red light. Calcium and cold water act slowly and undergo intense chemical reactions in hot water, releasing hydrogen gas (lithium, sodium, and potassium undergo intense chemical reactions even in cold water). Calcium is also easily combined with halogens, sulfur, nitrogen, etc.