Calcium (Ca)
Stable isotopes of calcium available from ISOFLEX
| Isotope | Z(p) | N(n) | Atomic Mass | Natural Abundance | Enrichment Level | Chemical Form |
| Ca-40 | 20 | 20 | 39.9625912 | 96.941% | 99.99% | Carbonate |
| Ca-42 | 20 | 22 | 41.9576183 | 0.647% | 68.00-96.80% | Carbonate |
| Ca-43 | 20 | 23 | 42.958767 | 0.135% | 62.20-90.00% | Carbonate |
| Ca-44 | 20 | 24 | 43.955481 | 2.086% | 94.50-99.00% | Carbonate |
| Ca-46 | 20 | 26 | 45.953693 | 0.004% | 15.90-24.80% | Carbonate |
| Ca-48 | 20 | 28 | 47.952533 | 0.187% | 64.00-97.10% | Carbonate |
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Calcium was discovered in 1808 by Sir Humphry Davy. Its name originates with the Latin word calx, meaning “lime.” Compounds such as lime were prepared by the Romans as early as the first century AD. Literature dating back to 975 AD indicates that plaster of Paris (calcium sulfate) is useful for setting bones.
A moderately soft, bright silver-white, crystalline metal, calcium oxidizes in air to form adherent protective film and can be machined, extruded or drawn. It is soluble in acid and decomposes in water to liberate hydrogen. It has a brick-red color when introduced to flame in a flame test.
Calcium metal reacts with a number of nonmetallic elements, forming their corresponding binary compounds. While the reaction with fluorine occurs at ambient temperatures, other elements combine only at elevated temperatures in the range of 300-900 ºC. Calcium reacts vigorously with water at ordinary temperatures, with the evolution of hydrogen. It is a strong reducing agent and can reduce most metal oxides and halides into their metals at elevated temperatures. It can reduce all the lower electropositive metals.
Applications of calcium are mostly found in metallurgy. It is used to produce alloys with aluminum, lead, beryllium, copper, silicon and other metals. It is also used as a desulfurizer, decarburizer and deoxidizer for ferrous and nonferrous alloys; for removal of bismuth from lead; and as a reducing agent for zirconium, uranium, thorium and other metals.
Properties of Calcium
| Name | Calcium |
| Symbol | Ca |
| Atomic number | 20 |
| Atomic weight | 40.078 |
| Standard state | Solid at 298 °K |
| CAS Registry ID | 7440-70-2 |
| Group in periodic table | 2 |
| Group name | Alkaline earth metal |
| Period in periodic table | 4 |
| Block in periodic table | s-block |
| Color | Silvery white |
| Classification | Metallic |
| Melting point | 851 °C |
| Boiling point | 1484 °C |
| Thermal conductivity | 200 W/(m·K) |
| Electrical resistivity | 3.43 µΩ·cm at 0 °C |
| Electronegativity | 1.0 |
| Specific heat | 0.647 J/g·K at 20 °C |
| Heat of vaporization | 155 kJ·mol-1 |
| Heat of fusion | 8.54 kJ·mol-1 |
| Density of solid | 1.54 g/cm3 |
| Electron configuration | [Ar]4s2 |
| Ionic radius | 1.06 Å (Ca2+) |
| Oxidation state | +2 |
| Standard electrode potential | Eº = -2.87V |
Research
- Calcium isotopes in caves as a proxy for aridity: Modern calibration and application to the 8.2 kyr event
- Soluble corn fiber can help young women build bone, and older women preserve bone
- Synthesis of new transuranium isotopes in multinucleon transfer reactions using a velocity filter
- Additive effects of acidification and mineralogy on calcium isotopes in Triassic/Jurassic boundary limestones
- The isotopic nature of the Earth’s accreting material through time
- Assessing human weaning practices with calcium isotopes in tooth enamel