All practice pages/Interatomic theory/Elements
Element 20, an alkaline earth metal
The metal in chalk, marble, bones and cement, and the most abundant metal in your body.
Period 4, group 2. The other alkaline earth metals are tinted, and every cell opens its own article.
Two valence electrons, which calcium gives up to form the Ca²⁺ ion in its compounds.
About 4% of the crust by mass, in limestone, chalk and marble (all calcium carbonate), gypsum and fluorite. Seashells and coral are calcium carbonate too, and about 1 kg of an adult's body is calcium, almost all of it in bones and teeth.
Humphry Davy isolated it in 1808 by electrolysis of a mixture of lime and mercury oxide. Lime itself had been made by heating limestone since ancient times. The name comes from the Latin calx, lime.
Cement and concrete depend on lime made from limestone, and plaster and drywall are gypsum. Calcium also refines steel, calcium chloride melts ice and settles dust on roads, and calcium carbonate is chalk, an antacid and a filler in paper, paint and toothpaste.