Calcium
Definition and meaning of Calcium in chemistry.
Calcium is a chemical element represented by the symbol Ca and atomic number 20. It is a reactive, silvery-gray metal that belongs to the alkaline earth metal group.
In more detail
Positioned in group 2 of the periodic table, calcium is a moderately hard and highly reactive alkaline earth metal located directly below magnesium. It is the fifth most abundant element in the Earth's crust, occurring massively in extensive sedimentary deposits of calcium carbonate such as natural limestone, chalk, and geological marble. Calcium is highly reactive chemically and readily forms a dark, protective oxide-nitride surface coating when exposed to atmospheric air, requiring careful storage in inert environments. It reacts steadily with liquid water to produce flammable hydrogen gas and basic calcium hydroxide, although the reaction is notably less violent than those of the alkali metals. In complex biological systems, calcium represents the most abundant metallic element, forming the rigid structural basis of vertebrate bones and teeth primarily as the mineral hydroxyapatite. Additionally, mobile calcium ions, denoted as Ca2+, act as vital intracellular messengers that stringently regulate muscle contraction, blood coagulation, and rapid nerve impulse transmission.
Key facts
| Field | General Chemistry |
|---|---|
| Symbol | Ca |
| Atomic number | 20 |
| Atomic mass | 40.078 u |
| Category | Alkaline Earth Metal |
| State at room temperature | Solid |
| Melting point | 842 °C (1548 °F) |
| Boiling point | 1484 °C (2703 °F) |
| Year discovered | 1808 |
Calcium carbonate is the primary constituent of limestone, which is heavily mined, crushed, and thermally processed to manufacture cement and concrete for the global construction industry.
Frequently asked questions
Where is calcium predominantly found in the human body?
Over 99 percent of the total calcium in the human body is stored directly within bones and teeth, providing them with essential structural strength and physical rigidity.
Does elemental calcium metal occur naturally on Earth?
No, because of its incredibly high chemical reactivity, calcium only exists naturally bound within chemical compounds, never freely isolated as a pure metal.