Updated by Reginald Davey 10/01/23
Calcium is the third most abundant metal in the earth’s crust. It is trimorphic in structure and its hardness is greater than that of sodium. It is less chemically reactive than alkaline metals. The atomic number of calcium is 20 and its chemical symbol is Ca.
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Calcium is extremely abundant and is found in almost every environment across the globe. It is essential for the growth of plants and animals.
Calcium is not available alone in nature, it is found in the form of limestone, gypsum, and fluorite. It is the most abundant metal present in the human body. Aquatic life is affected by the presence of its compound, calcium phosphide.
Biological Role
Calcium plays several critical roles in biological systems. It is a major constituent of bones and teeth, providing structure and strength. Calcium carbonate provides structural rigidity in shells and exoskeletons.
In vertebrates such as mammals and fish, hydroxyapatite crystals, which are a form of calcium phosphate, are responsible for skeletal structure. These crystals are found in collagen. On the surface of bones, calcium ions interact with calcium ions in the bodily fluids, which enables ion exchange. This ion exchange maintains calcium balance in both bones and blood.
Calcium enters the extracellular fluid via the gastrointestinal tract and can become available via the process of bone resorption. In the extracellular fluid, calcium reservoirs help to circulate calcium, making it available for biological processes.
Calcium is used for several key biological processes such as nerve signal transmission, muscle contraction, coagulation, and hormone signaling.
In plants, calcium is an essential nutrient. A major use of calcium is in cell walls and membranes, which is provided in the form of calcium pectate. It also provides rigidity and is used in the biosynthesis of starch and cellulose. In the vacuole, it is used as a counter-cation and also finds application in plant cytosol as an intracellular messenger.
Chemical Properties of Calcium
The chemical properties of calcium are provided in the table below:
| Chemical Data |
| CAS number |
7440-70-2 |
| Thermal neutron cross section |
0.43 barns/atom |
| Electrode potential |
-2.80 V |
| Ionic radius |
0.990 Å |
| Electro negativity |
1 |
| X-ray absorption edge |
3.07016 Å |
| Electrochemical equivalent |
0.747 g/A/h |
Physical Properties
The following table discusses the physical properties of calcium.
| Properties |
Metric |
Imperial |
| Density |
1.54 g/cm3 |
0.055 lb/in3 |
| Melting point |
837-841 °C |
1540-1550 °F |
| Boiling point |
1484°C |
2703°F |
Mechanical Properties of Calcium
The mechanical properties of calcium are tabulated below.
| Properties |
Metric |
Imperial |
| Tensile Strength |
110 MPa |
16000 psi |
| Modulus of elasticity |
23.4 GPa |
3390 ksi |
| Shear modulus |
7.38 GPa |
1070 ksi |
| Hardness, Vickers |
17 |
17 |
| Elongation at Break |
7% |
7% |
| Poissons Ratio |
0.31 |
0.31 |
Thermal Properties of Calcium
The thermal properties of calcium are tabulated below.
| Properties |
Metric |
Imperial |
| Thermal expansion co-efficient (@20°C/68°F) |
22.15 µm/m°C |
22.15 µin/in°F |
| Thermal conductivity |
126 W/mK |
874 BTU in/hr.ft².°F |
Commercial and Industrial Applications of Calcium
Calcium is used in several industrial and commercial applications.
Calcium is used in metal extraction as a reducing agent and as an alloying agent for the production of certain industrial metals. It is also used as a decarbonizer, desulfurizer, and deoxidizer.
In the food industry, calcium gluconate is an important food additive, and it is used in cheese and dairy manufacture and as a supplement in animal feeds, and as a fertilizer ingredient. It is also commonly added to mineral supplements and toothpaste.
Another use is in insecticides and rodenticides. Calcium arsenate is commonly used as an insecticide, with calcium phosphide used in rodenticides. Furthermore, calcium-containing compounds find widespread application in fireworks, cement and mortar, blackboard chalk, cosmetics, acetylene gas, plastics, and paints.
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