Calcium (Ca)

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Name: Calcium
Symbol: Ca
Atomic Number: 20
Atomic Mass: 40.078 amu
Melting Point: 839.0 °C (1112.15 K, 1542.2 °F)
Boiling Point: 1484.0 °C (1757.15 K, 2703.2 °F)
Number of Protons/Electrons: 20
Number of Neutrons: 20
Classification: [[../groups/alkaline.html|Alkaline Earth]]
Crystal Structure: Cubic
Density @ 293 K: 1.55 g/cm3
Color: Silvery

Atomic Structure



Number of Energy Levels: 4
First Energy Level: 2
Second Energy Level:8
Third Energy Level: 8
Fourth Energy Level:2

Isotopes

Isotope
Half Life
Ca-40
Stable
Ca-41
103000.0 years
Ca-42
Stable
Ca-43
Stable
Ca-44
Stable
Ca-45
162.7 days
Ca-46
Stable
Ca-47
4.5 days
Ca-48
Stable
Ca-49
8.7 minutes

Facts

Date of Discovery: 1808
Discoverer: Sir Humphrey Davy
Name Origin: From the latin word calcis (lime)
Uses: life forms for bones and shells
Obtained From: chalk, limestone, marble. 3.5% of crust



Calcium is essential for living organisms, in particular in cell physiology, a major material used in mineralization of bones and shells. It is the most abundant metal by mass in many animals.
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Calcium is an important component of a healthy diet and a mineral necessity for life. The RDA recommends getting 1000mg of calcium a day.
Many good sources of calcium exist, including seaweeds such as kelp, wakame and hijiki, dairy products such as milk, cheese, butter; and fortified products such as orange juice and soy milk. Calcium is good for you and easily added in any diet, except for vegans.


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5th most abundant element by mass in the earth's crust. Alpha helix is the shape that it comes in as well.
  • as a reducing agent in the extraction of other metals
  • as a deoxidizer
  • production of aluminum, lead, copper
  • in the making of cements to be used in construction
  • in the making of cheese where calcium influence the activity of rennin in bringing about the coagulation of milk.
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Especially important for women over 50 as women start to lose their bone mass and they start to become softer, so to speak. Getting extra calcium can be found in the form of milk, cheese, yogurt and other dairy products as well as certain meats and vegetables.

Isotopes

Calcium has four stable isotopes (40Ca, 42Ca, 43Ca and 44Ca), plus two more isotopes (46Ca and 48Ca) that have such long half-lives that for all practical purposes they also can be considered stable. The 20% range in relative mass among naturally occurring calcium isotopes is greater than for any element except hydrogen and helium. Calcium also has a cosmogenic isotope, radioactive 41Ca, which has a half-life of 103,000 years.
The most abundant isotope, 40Ca, has a nucleus of 20 protons and 20 neutrons. This is the heaviest stable isotope of any element that has equal numbers of protons and neutrons. In supernova explosions, calcium is formed from the reaction of carbon with various numbers of alpha particles (helium nuclei), until the most common calcium isotope (containing 10 helium nuclei) has been synthesized.

Geochemical Cycling


Calcium provides an important link between tectonics, climate and the carbon cycle. In the simplest terms, uplift of mountains exposes Ca-bearing rocks to chemical weathering and releases Ca2+ into surface water.
The result is that each Ca2+ ion released by chemical weathering ultimately removes one CO2 molecule from the surficial system (atmosphere, ocean, soils and living organisms), storing it in carbonate rocks where it is likely to stay for hundreds of millions of years.

Characteristics



In chemical terms, calcium is reactive and soft for a metal (though harder than lead, it can be cut with a knife with difficulty). It is a silvery metallic element that must be extracted by electrolysis from a fused salt like calcium chloride. Once produced, it rapidly forms a gray-white oxide and nitride coating when exposed to air. In bulk form (typically as chips or "turnings"), the metal is somewhat difficult to ignite, more so even than magnesium chips; but, when lit, the metal burns in air with a brilliant high-intensity orange-red light. Calcium metal reacts with water, evolving hydrogen gas at a rate rapid enough to be noticeable, but not fast enough at room temperature to generate much heat. In powdered form, however, the reaction with water is extremely rapid, as the increased surface area of the powder accelerates the reaction with the water. Part of the slowness of the calcium-water reaction results from the metal being partly protected by insoluble white calcium hydroxide. In water solutions of acids, where this salt is soluble, calcium reacts vigorously.

Calcium, with a density of 1.55 g/cm3, is the lightest of the alkaline earth metals; magnesium (1.74) and beryllium (1.84) are more dense, although lighter in atomic mass. From strontium onward, the alkali earth metals become more dense with increasing atomic mass.


History


Lime as building material was used since prehistoric times going as far back as 7000 to 14000 BC. The first dated lime kiln dates back to 2500 BC and was found in Khafajah Mesopotamia. Calcium was known as early as the first century when the Ancient Romans prepared lime as calcium oxide. Literature dating back to 975 AD notes that Plaster of paris (calcium sulfate), is useful for setting broken bones. It was not isolated until 1808 in England when Sir Humphrey Davis electrolyzed a mixture of lime and mercuric oxide.Davy was trying to isolate calcium; when he heard that Swedish chemist and Pontin prepared calcium amalgam by electrolyzing lime in mercury, he tried it himself. He worked with electrolysis throughout his life and also discovered/isolated sodium, potassium, magnesium, boron and barium. Calcium metal was not available in large scale until the beginning of the 20th century.

Co-factor in some enzymes, component of bones

Uses of Calcium
  • reducing agent for the preparation of metals such as thorium, uranium, zirconium, etc.
  • deoxidiser, desulphurizer, or decarbonizer for various alloys
  • alloys of calcium with agent for aluminium, beryllium, copper, lead, and magnesium have some useful properties
  • "getter" for residual gases in vacuum tubes, etc.
  • quicklime (CaO) is made by heating limestone (CaCO3) and changes into slaked lime, Ca(OH)2, on the addition of water. It is a cheap base for the chemical industry with many uses.
  • calcium from limestone is a component of Portland cement. Mixed with sand it hardens as mortar and plaster while taking up carbon dioxide from the air
  • the solubility of the carbonate in water containing carbon dioxide results in stalactites and stalagmites (Cheddar Gorge) and hardness in water


10 important facts about calcium:
  1. Calcium isn't found free in nature, but it can be purified into a soft silvery-white alkaline earth metal.
  2. Calcium is the 5th most abundant element in the Earth's crust, present at a level of about 3% in the oceans and soil.
  3. The element is essential for animal and plant nutrition. Calcium participates in many biochemical reactions, including building skeletal systems and moderating muscle action.
  4. Vitamin D is essential for calcium absorption by the human body. Vitamin D is converted to a hormone which causes intestinal proteins responsible for calcium absorption to be produced.
  5. While calcium and its compounds are not considered to be toxic, ingesting too many calcium carbonate dietary supplements or antacids can cause milk-alkali syndrome, which is associated with hypercalcemia sometimes leading to fatal renal failure. Excessive consumption would be on the order of 10 g calcium carbonate/day, though symptoms have been reported upon ingesting as little as 2.5 g calcium carbonate daily.
  6. Calcium is used for making cement, making cheese, removing nonmetallic impurities from alloys, and as a reduction agent in the preparation of other metals.
  7. Pure calcium metal reacts vigorously and sometimes violently with water and acids.
  8. The element name "calcium" comes from the Latin word "calcis" meaning "lime".
  9. Calcium has been known since the 1st century, when the ancient Romans were known to make lime from calcium oxide.
  10. Though calcium has been known for thousands of years, it was not purifed as an element until 1808 by Sir Humphrey Davy.