| Calcium is the chemical element in the periodic table | | | | sand, it hardens into a mortar and is turned into plaster |
| that has the symbol Ca and atomic number 20. | | | | by carbon dioxide uptake. |
| Calcium is a soft grey alkaline earth metal that is used | | | | Mixed with other compounds, lime forms an important |
| as a reducing agent in the extraction of thorium, | | | | part of Portland cement. |
| zirconium and uranium. Calcium is also the fifth most | | | | When water percolates through limestone or other |
| abundant element in the Earth's crust. It is essential for | | | | soluble carbonate rocks, it partially dissolves part of the |
| living organisms, particularly in cell physiology, and is the | | | | rock and causes cave formation and characteristic |
| most common metal in many animals. | | | | stalactites and stalagmites and also forms hard water. |
| Notable characteristics Calcium is a rather soft, grey, | | | | Other important calcium compounds are nitrate, sulfide, |
| metallic element that can be extracted by electrolysis | | | | chloride, carbide, cyanamide, and hypochlorite. |
| from calcium fluoride. It burns with a yellow-red flame | | | | Isotopes Calcium has four stable isotopes (40Ca and |
| and forms a white nitride coating when exposed to air. | | | | 42Ca through 44Ca), plus two more isotopes (46Ca |
| It reacts with water, displacing hydrogen and forming | | | | and 48Ca) that have such long half-lives that for all |
| calcium hydroxide. | | | | practical purposes they can be considered stable. |
| Calcium is essential in muscle contraction, oocyte | | | | It also has a cosmogenic isotope, radioactive 41Ca, |
| activation, building strong bones and teeth, blood | | | | which has a half-life of 103,000 years. Unlike |
| clotting, nerve impulse transmission, regulating | | | | cosmogenic isotopes that are produced in the |
| heartbeat, and fluid balance within cells. In the U.S., | | | | atmosphere, 41Ca is produced by neutron activation of |
| between about 50% and 75% of adults do not get | | | | 40Ca. Most of its production is in the upper metre or |
| sufficient calcium in their diet. Adults need between | | | | so of the soil column where the cosmogenic neutron |
| 1,000 and 1,300 mg of calcium in their daily diet. | | | | flux is still sufficiently strong. 41Ca has received much |
| The most abundant isotope, 40Ca, has a nucleus of 20 | | | | attention in stellar studies because it decays to 41K, a |
| protons and 20 neutrons. | | | | critical indicator of solar-system anomalies. |
| Its electron configuration is: 2 electrons in the K shell | | | | Naturally occurring calcium is 97% in the form of 40Ca. |
| (principal quantum number 1), 8 in the L shell (principal | | | | 40Ca is one of the daughter products of 40K decay, |
| quantum number 2), 8 in the M shell (principal quantum | | | | along with 40Ar. While K-Ar dating has been used |
| number 3), and 2 in the N shell (principal quantum | | | | extensively in the geological sciences, the prevalence |
| number 4). The outer shell is the valence shell, with 2 | | | | of 40Ca in nature has impeded its use in dating. |
| electrons in the lone 4s orbital, the 3p orbitals being | | | | Techniques using mass spectrometry and a double |
| empty. | | | | spike isotope dilution have been used for K-Ca age |
| Occurrence Calcium is not naturally found in its | | | | dating. |
| elemental state. Calcium is found mostly in soil systems | | | | Dietary calcium supplements There are conflicting |
| as limestone, gypsum and fluorite. Stalagmites and | | | | recommendations about when to take calcium |
| stalactites contain calcium carbonate. Being an | | | | supplements. |
| essential macromineral in the human diet, soil | | | | However, most experts agree that no more than 500 |
| conservation practices often consider the sustainable | | | | mg should be taken at a time – any excess |
| equilibrium of calcium concentrations in the earth. | | | | will go to waste. It is recommended to spread doses |
| Applications Calcium is an important component of a | | | | throughout the day, with the last dose near bedtime. |
| healthy diet. A deficit can affect bone and tooth | | | | Recommended daily calcium intake varies from 1000 |
| formation, while overretention can cause kidney | | | | to 1500 milligrams, depending upon the stage of life. |
| stones. Vitamin D is needed to absorb calcium. Dairy | | | | Calcium carbonate is the most common and least |
| products, such as milk and cheese, are a well-known | | | | expensive calcium supplement. It can be difficult to |
| source of calcium. However, some individuals are | | | | digest and causes gas in some people. Taking |
| allergic to dairy products and even more people, | | | | magnesium with it can help to prevent constipation. |
| particularly those of non-European descent, are | | | | Calcium carbonate is 40% elemental calcium. 1000 mg |
| lactose-intolerant, leaving them unable to consume | | | | will provides 400 mg of calcium. Take this supplement |
| dairy products. | | | | with food to aid in absorption. |
| Fortunately, many other good sources of calcium exist. | | | | Calcium citrate is more easily absorbed, easier to |
| These include: seaweeds such as kelp, wakame and | | | | digest and less likely to cause constipation and gas |
| hijiki; nuts and seeds (like almonds and sesame); beans; | | | | than calcium carbonate. It also has a lower risk of |
| seafood such as oysters and shrimp; soft-boned fish; | | | | contributing to the formation of kidney stones. Calcium |
| amaranth; whole wheat; collard greens; okra; rutabaga; | | | | citrate is 21% elemental calcium. 1000 mg will provide |
| broccoli; and fortified products such as orange juice | | | | 210 mg of calcium. It is more expensive than calcium |
| and bread. | | | | carbonate and more of it must be taken to get the |
| Other uses include: as a reducing agent in the | | | | same amount of calcium. |
| extraction of other metals, such as uranium, zirconium, | | | | Calcium phosphate costs more than calcium |
| and thorium. | | | | carbonate, but less than calcium citrate. It is easily |
| as a deoxidizer, desulfurizer, or decarbonizer for | | | | absorbed and is less likely to cause constipation and |
| various ferrous and nonferrous alloys. | | | | gas than either. |
| as an alloying agent used in the production of | | | | Calcium lactate and calcium aspartate are both more |
| aluminium, beryllium, copper, lead, and magnesium alloys. | | | | easily digested, but more expensive than calcium |
| in the making of cements and mortars to be used in | | | | carbonate. |
| construction. | | | | Disorders of calcium metabolism occur when the body |
| History Calcium (Latin calcis, meaning "lime") was | | | | has too little or too much calcium. The serum level of |
| known as early as the first century when the Ancient | | | | calcium is closely regulated within a fairly limited range |
| Romans prepared lime as calcium oxide. It was not | | | | in the human body. |
| actually isolated until 1808 in England when Sir | | | | The amount of biologically active calcium varies with |
| Humphrey Davy electrolyzed a mixture of lime and | | | | the level of albumin, a protein to which calcium is bound, |
| mercuric oxide. Davy was trying to isolate calcium and | | | | and therefore levels of ionized calcium are better |
| when he heard that Berzelius and Pontin prepared | | | | measures than a total calcium; however, one can |
| calcium amalgam by electrolyzing lime in mercury, he | | | | correct a total calcium if the albumin level is known. |
| tried it himself. He worked with electrolysis throughout | | | | When you don't have enough calcium your bones |
| his life and also discovered/isolated magnesium, | | | | become weak and very fragile. |
| strontium and barium. | | | | A normal ionized calcium is 1.12-1.45 mmol/L (4.54-5.61 |
| Compounds Calcium, combined with phosphate to | | | | mg/dL). |
| form hydroxylapatite, is the mineral portion of human | | | | A normal total calcium is 2.2-2.6 mmol/L (9-10.5 mg/dl). |
| and animal bones and teeth. The mineral portion of | | | | Total calcium of less than 8.0 mg/dL is hypocalcaemia, |
| some corals can also be transformed into | | | | with levels below 1.59 mmol/L (6 mg/dL) generally fatal. |
| hydroxylapatite. | | | | Total calcium of more than 11.111 mg/dL is |
| Calcium oxide (lime) is used in many chemical refinery | | | | hypercalcaemia, with levels over 3.753 mmol/L (15.12 |
| processes and is made by heating and carefully | | | | mg/dL) generally fatal. |
| adding water to limestone. When lime is mixed with | | | | |