Calcium
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| General |
| Name, Symbol, Number | Calcium, Ca, 20 |
| Series | Alkaline earth metal |
| Group, Period, Block | 2 (IIA), 4, s |
| Density, Hardness | 1550 kg/m3, 1.75 |
| Appearance | silvery white
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| Atomic Properties |
| Atomic weight | 40.078 amu |
| Atomic radius (calc.) | 180 (194) pm |
| Covalent radius | 174 pm |
| van der Waals radius | no information |
| Electron configuration | [Ar]4s2 |
| e- 's per energy level | 2, 8, 8, 2 |
| Oxidation states (Oxide) | 2 (strong base) |
| Crystal structure | Cubic face centered |
| Physical Properties |
| State of matter | solid (paramagnetic) |
| Melting point | 1115 K (1548°F) |
| Boiling point | 1757 K (2703°F) |
| Molar volume | 26.20 ×10-6 m3/mol |
| Heat of vaporization | 153.6 kJ/mol |
| Heat of fusion | 8.54 kJ/mol |
| Vapor pressure | 254 Pa at 1112 K |
| Speed of sound | 3810 m/s at 293.15 K |
| Other |
| Electronegativity | 1.00 (Pauling scale) |
| Specific heat capacity | 0.632 J/(kg*K) |
| Electrical conductivity | 29.8 106/m ohm |
| Thermal conductivity | 201 W/(m*K) |
| 1st ionization potential | 589.8 kJ/mol |
| 2nd ionization potential | 1145.4 kJ/mol |
| 3rd ionization potential | 4912.4 kJ/mol |
| Most Stable Isotopes |
| iso | NA | half-life | DM | DE MeV | DP |
| 40Ca | 96.941% | Ca is stable with 20 neutrons |
| 41Ca | {syn.} | 103,000y | epsilon | 0.421 | 41K |
| 42Ca | 0.647% | Ca is stable with 22 neutrons |
| 43Ca | 0.135% | Ca is stable with 23 neutrons |
| 44Ca | 2.086% | Ca is stable with 24 neutrons |
| 46Ca | 0.004% | Ca is stable with 26 neutrons |
| 48Ca | 0.187% | >6×1018y | beta- | 4.272 | 48Ti |
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| SI units & STP are used except where noted. |
Calcium is a chemical element in the periodic table that has the symbol Ca and atomic number 20.
Calcium is a soft grey alkaline earth metal that is used as a reducing agent in the extraction of
thorium, zirconium and uranium. This element is also the fifth most abundant element in the earth's crust. It is essential for living organisms, particularly in cell physiology.
Notable Characteristics
Calcium is a rather hard element that is purified by electrolysis from calcium fluoride that burns with a yellow-red flame and forms a white nitride coating when exposed to air. It reacts with water displacing hydrogen and forming calcium hydroxide.
Applications
Calcium is an important component of a healthy diet. Its minor deficit can affect bone and teeth formation. Its excess can lead to kidney stones. Vitamin D is needed to absorb calcium. Dairy products are an excellent source of calcium.
For more information about Ca in living nature see Ca (biology)
Other uses include:
- Reducing agent in the extraction of other metals such as uranium, zirconium, and thorium.
- Deoxidizer, desulfurizer, or decarburizer for various ferrous and nonferrous alloys.
- Alloying agent used in the production of aluminum, beryllium, copper, lead, and magnesium alloys.
History
(Latin calx, lime) Lime was prepared and used by the Romans as early as the 1st century, but
calcium was not discovered until 1808. After learning that Berzelius and Pontin prepared calcium amalgam by electrolyzing lime in mercury, Sir Humphry Davy was able to isolate the impure metal.
Occurrence
Calcium is the fifth most abundant element in the earth's crust (forming more than 3%) and is an essential part of leaves, bones, teeth, and shells. Due to its chemical reactivity with air and water, calcium is never found in nature unbound to other elements, except in living organisms where Ca2+ plays a key role in cell physiology. This metallic element is found in quantity in limestone, gypsum, and fluorite. Apatite is the fluorophosphate or chlorophosphate of calcium. Electrolysis of molten calcium chloride (CaCl2) can be used to isolate pure calcium.
Isolation (* follow):
cathode: Ca2+* + 2e- --> Ca
anode: Cl-* --> ½Cl2 (gas) + e-
Compounds
Quicklime (CaO) is used in many chemical refinery processes and is made by heating and carefully adding water to limestone. When CaO is mixed with sand it hardens into a mortar and is turned into plaster by carbon dioxide uptake. Mixed with other compounds, CaO forms an important part of Portland cement.
When water percolates through limestone or other soluble carbonate rocks, it partially disolves part of the rock and causes cave formation and characteristic stalactites and stalagmites and also forms hard water. Other important calcium compounds are nitrate, sulfide, chloride, carbide, cyanamide, and hypochlorite.
Isotopes
Calcium has six stable isotopes, two of which occur in nature: stable Ca-40 and radioactive Ca-41 with a half-life = 103,000 years. 97% of the element is in the form of Ca-40. Ca-40 is one of the daughter products of K-40 decay, along with Ar-40. While K-Ar dating has been used extensively in the geological sciences, the prevalence of Ca-40 in nature has impeded its use in dating. Techniques using mass spectrometry and a double spike isotope dilution have been used for K-Ca age dating. Unlike cosmogenic isotopes that are produced in the atmosphere, Ca-41 is produced by neutron activation of Ca-40. Most of its production is in the upper meter or so of the soil column where the cosmogenic neutron flux is still sufficiently strong. Ca-41 has received much attention in stellar studies because Ca-41 decays to K-41, a critical indicator of solar-system anomalies.
External Links
Referenced By
Acronym/Medical List | Alkali earth metal | Alkali earth metals | Alkaline Earth | Alkaline Earth metals | Alkaline earth metal | Antacid | Apatite | Apple/Nutritional information | Black-eyed peas | Ca (biology) | Ca ion (physiology) | Calcium Carbonate | Calcium hydroxide | Calcium in biology | Carbon dioxide | Chemical pathology | Dietary mineral | Discoveries of the chemical elements | Discovery of the chemical elements | Electromagnetic spectroscopy | Electron orbital | Electronegative | Electronegativity | Europium | Fraunhofer line | Gadolinium | Goldschmidt Classification | Group 2 | Group 2 element | Heat of vaporization | Hemolymph | Isotope table (complete) | Isotope table (divided) | Kalium | List of chemistry topics | List of compounds | List of compounds without articles | List of human blood components | List of medical abbreviations | List of medical acronyms | List of stable isotopes | Luna | Magnesium | Moon | Mulliken scale | Nutritional information about the apple | Pauling Electronegativity Scale | Periodic Table | Periodic Table of the Elements | Periodic table/Alternate Table | Periodic table/Electron configurations | Periodic table/Metals and Non Metals | Periodic table/Standard Table | Periodic table/Table only | Periodic table (alternate) | Periodic table (block) | Periodic table (electron configurations) | Periodic table (metals and non-metals) | Periodic table (standard) | Periodic table of elements | Periodic table of the chemical elements | Plant nutrition | Potassium | Rubidium-Strontium dating | Rubidum-Strontium dating | Scandium | Sea water | Spirulina | Sprouting | Strontium | Strontium 90 | Sulfide | Sulfides | Terbium | Timeline of chemical element discovery | Trace mineral | Valency | Vaporization heat
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