Ca • Atomic number 20
Calcium
Calcium is a reactive alkaline-earth metal with the chemical symbol Ca. It is abundant in the Earth’s crust but is never found as a free metal because it reacts readily with oxygen, water and other elements. Important minerals include limestone, gypsum and fluorite.
Metallic calcium is used as a reducing, deoxidising and desulfurising agent in metallurgy and as an alloying addition. Calcium compounds are essential in construction materials, agriculture, chemical production and many biological processes.
The metal is produced from purified calcium compounds, for example by electrolysis or metallothermic reduction. Because metallic calcium reacts quickly with air and moisture, production and packaging take place under controlled conditions.
Calcium metal must be kept dry and protected from air. Contact with water releases heat and hydrogen. Suitable dry extinguishing agents must be used for metal fires; water and carbon dioxide are unsuitable.
The technical assessment of a material always depends on purity, chemical form, particle size, packaging and intended use.