Calcium
Definition and meaning of Calcium in chemistry.
![Calcium element card: symbol Ca, atomic number 20, atomic mass 40.078, electron configuration [Ar] 4s², oxidation states +2, Alkaline earth metal, group 2, period 4, solid at room temperature.](/assets/images/terms/calcium-chemical-element.webp)
Calcium is a chemical element represented by the symbol Ca and atomic number 20. This reactive, silvery-gray metal belongs to the alkaline earth metal group on the periodic table.
In more detail
Calcium is a moderately hard alkaline earth metal located in group 2 of the periodic table. It is a highly reactive substance that sits directly below magnesium on the chemical chart. Calcium ranks as the fifth most abundant element found within the Earth's solid crust.
It occurs massively in extensive sedimentary rock deposits composed of calcium carbonate. These familiar natural rock formations include common limestone, soft chalk, and geological marble. Pure calcium metal readily forms a dark surface coating when exposed to atmospheric air.
This protective oxide and nitride layer forms quickly upon contact with oxygen and nitrogen. Because of this reactivity, chemists must store the pure metal in specialized inert environments. Calcium reacts steadily with liquid water to produce flammable hydrogen gas and basic calcium hydroxide.
However, this water reaction remains notably less violent than the explosive reactions of alkali metals. In complex biological systems, calcium represents the single most abundant metallic element present. It provides the essential rigid structural framework for vertebrate bones and animal teeth.
The human body builds these strong structures primarily using a hard calcium mineral called hydroxyapatite. Mobile calcium ions, written as Ca2+, also act as vital chemical messengers inside living cells. These highly important ions tightly regulate muscle contractions, blood clotting, and rapid nerve impulse transmission.
Key facts
| Field | General Chemistry |
|---|---|
| Symbol | Ca |
| Atomic number | 20 |
| Atomic mass | 40.078 u |
| Category | Alkaline-Earth-Metal |
| Melting point | 842 °C (1548 °F) |
| Year discovered | 1808 |
Calcium carbonate serves as the primary chemical constituent found inside natural limestone rock. Industrial workers heavily mine, crush, and thermally process this incredibly common sedimentary rock. Factories use the processed limestone 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. This mineral provides them with essential structural strength and physical rigidity.
Does elemental calcium metal occur naturally on Earth?
No, calcium only exists naturally bound within chemical compounds. Its incredibly high chemical reactivity prevents it from ever forming naturally as a pure, isolated metal.
Related terms
Sources & references
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