Calcium

Calcium belongs to the alkaline earth metals. In its elemental form it is a metalic solid. The alkaline earth metals easily liberate two electrons, forming twofold positively charged ions. The violent reaction with water results in the formation of molecular hydrogen (H₂) and OH^-. Calcium is a constituent of many minerals, respective carbonates for example make part of limestone and chalk, the sulfate is forming gypsum and the phosphate is forming apatit.