Short answers, pulled from the story.
Humphry Davy isolated calcium as a pure silvery metal in the year 1808. This discovery occurred in the early nineteenth century, although calcium compounds like lime and plaster were used by ancient builders in Mesopotamia and Egypt as early as 7000 BC.
A calcium atom possesses 20 electrons arranged in a configuration of [Ar]4s with two valence electrons in the outermost s-orbital. This specific electron arrangement allows calcium to form ionic compounds that are almost always divalent and creates a lattice energy significantly higher than hypothetical univalent salts.
Calcium ions released from weathered rocks react with dissolved carbon dioxide to form limestone, effectively scrubbing carbon dioxide from the atmosphere and ocean. This geochemical cycle stores carbon in carbonate rocks for geological epochs and exerts a strong long-term effect on global climate.
Calcium ions function as a vital electrolyte that regulates muscle contraction, nerve conduction, and blood clotting. The element is indispensable for the formation of hydroxyapatite, the mineral component of bone, and supports the synthesis and function of blood cells.
Calcium is produced in the United States and Canada by reducing lime with aluminum at high temperatures. This process creates 24 to 34 kilogram pieces of metal that are distilled for high purity and used in applications such as maintenance-free automotive batteries.
The U.S. Institute of Medicine and the European Food Safety Authority recommend 700 milligrams per day for children aged 1 to 3 years and 1300 milligrams for adolescents aged 9 to 18 years. These tolerable upper intake levels are set to prevent adverse side effects such as calcification of arteries and kidney stones.