Search This Blog

Monday, March 18, 2019

Calcium

From Wikipedia, the free encyclopedia

Calcium,  20Ca
Calcium unter Argon Schutzgasatmosphäre.jpg
Calcium
Appearancedull gray, silver; with a pale yellow tint
Standard atomic weight Ar, std(Ca)40.078(4)
Calcium in the periodic table
Hydrogen
Helium
Lithium Beryllium
Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium
Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium
Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium

Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson
Mg

Ca

Sr
potassiumcalciumscandium
Atomic number (Z)20
Groupgroup 2 (alkaline earth metals)
Periodperiod 4
Blocks-block
Element category  alkaline earth metal
Electron configuration[Ar] 4s2
Electrons per shell
2, 8, 8, 2
Physical properties
Phase at STPsolid
Melting point1115 K ​(842 °C, ​1548 °F)
Boiling point1757 K ​(1484 °C, ​2703 °F)
Density (near r.t.)1.55 g/cm3
when liquid (at m.p.)1.378 g/cm3
Heat of fusion8.54 kJ/mol
Heat of vaporisation154.7 kJ/mol
Molar heat capacity25.929 J/(mol·K)
Vapour pressure
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 864 956 1071 1227 1443 1755
Atomic properties
Oxidation states+1, +2 (a strongly basic oxide)
ElectronegativityPauling scale: 1.00
Ionisation energies
  • 1st: 589.8 kJ/mol
  • 2nd: 1145.4 kJ/mol
  • 3rd: 4912.4 kJ/mol
Atomic radiusempirical: 197 pm
Covalent radius176±10 pm
Van der Waals radius231 pm
Color lines in a spectral range
Spectral lines of calcium
Other properties
Natural occurrenceprimordial
Crystal structureface-centred cubic (fcc)
Face-centered cubic crystal structure for calcium
Speed of sound thin rod3810 m/s (at 20 °C)
Thermal expansion22.3 µm/(m·K) (at 25 °C)
Thermal conductivity201 W/(m·K)
Electrical resistivity33.6 nΩ·m (at 20 °C)
Magnetic orderingdiamagnetic
Magnetic susceptibility+40.0·10−6 cm3/mol
Young's modulus20 GPa
Shear modulus7.4 GPa
Bulk modulus17 GPa
Poisson ratio0.31
Mohs hardness1.75
Brinell hardness170–416 MPa
CAS Number7440-70-2
History
Discovery and first isolationHumphry Davy (1808)
Main isotopes of calcium
Iso­tope Abun­dance Half-life (t1/2) Decay mode Pro­duct
40Ca 96.941% stable
41Ca trace 1.03×105 y ε 41K
42Ca 0.647% stable
43Ca 0.135% stable
44Ca 2.086% stable
45Ca syn 162.7 d β 45Sc
46Ca 0.004% stable
47Ca syn 4.5 d β 47Sc
γ
48Ca 0.187% 6.4×1019 y ββ 48Ti

Calcium is a chemical element with symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to its heavier homologues strontium and barium. It is the fifth most abundant element in Earth's crust and the third most abundant metal, after iron and aluminium. The most common calcium compound on Earth is calcium carbonate, found in limestone and the fossilised remnants of early sea life; gypsum, anhydrite, fluorite, and apatite are also sources of calcium. The name derives from Latin calx "lime", which was obtained from heating limestone.

Some calcium compounds were known to the ancients, though their chemistry was unknown until the seventeenth century. Pure calcium was isolated in 1808 via electrolysis of its oxide by Humphry Davy, who named the element. Calcium compounds are widely used in many industries: in foods and pharmaceuticals for calcium supplementation, in the paper industry as bleaches, as components in cement and electrical insulators, and in the manufacture of soaps. On the other hand, the metal in pure form has few applications due to its high reactivity; still, in small quantities it is often used as an alloying component in steelmaking, and sometimes, as a calcium–lead alloy, in making automotive batteries.

Calcium is the most abundant metal and the fifth-most abundant element in the human body. As electrolytes, calcium ions play a vital role in the physiological and biochemical processes of organisms and cells: in signal transduction pathways where they act as a second messenger; in neurotransmitter release from neurons; in contraction of all muscle cell types; as cofactors in many enzymes; and in fertilization. Calcium ions outside cells are important for maintaining the potential difference across excitable cell membranes as well as proper bone formation.

Characteristics

Classification

Calcium is a very ductile silvery metal (sometimes described as pale yellow) whose properties are very similar to the heavier elements in its group, strontium, barium, and radium. A calcium atom has twenty electrons, arranged in the electron configuration [Ar]4s2. Like the other elements placed in group 2 of the periodic table, calcium has two valence electrons in the outermost s-orbital, which are very easily lost in chemical reactions to form a dipositive ion with the stable electron configuration of a noble gas, in this case argon. Hence, calcium is almost always divalent in its compounds, which are usually ionic. Hypothetical univalent salts of calcium would be stable with respect to their elements, but not to disproportionation to the divalent salts and calcium metal, because the enthalpy of formation of MX2 is much higher than those of the hypothetical MX. This occurs because of the much greater lattice energy afforded by the more highly charged Ca2+ cation compared to the hypothetical Ca+ cation.

Calcium, strontium, barium, and radium are always considered to be alkaline earth metals; the lighter beryllium and magnesium, also in group 2 of the periodic table, are often included as well. Nevertheless, beryllium and magnesium are significantly different from the other members of the group in their physical and chemical behaviour: they behave more like aluminium and zinc respectively and have some of the weaker metallic character of the post-transition metals, which is why the traditional definition of the term "alkaline earth metal" excludes them. This classification is mostly obsolete in English-language sources, but is still used in other countries such as Japan. As a result, comparisons with strontium and barium are more germane to calcium chemistry than comparisons with magnesium.

Physical

Calcium metal melts at 842 °C and boils at 1494 °C; these values are higher than those for magnesium and strontium, the neighbouring group 2 metals. It crystallises in the face-centered cubic arrangement like strontium; above 450 °C, it changes to an anisotropic hexagonal close-packed arrangement like magnesium. Its density of 1.55 g/cm3 is the lowest in its group. Calcium is harder than lead but can be cut with a knife with effort. While calcium is a poorer conductor of electricity than copper or aluminium by volume, it is a better conductor by mass than both due to its very low density. While calcium is infeasible as a conductor for most terrestrial applications as it reacts quickly with atmospheric oxygen, its use as such in space has been considered.

Chemical

Structure of the polymeric [Ca(H2O)6]2+ center in hydrated calcium chloride, illustrating the high coordination number typical for calcium complexes.
 
The chemistry of calcium is that of a typical heavy alkaline earth metal. For example, calcium spontaneously reacts with water more quickly than magnesium and less quickly than strontium to produce calcium hydroxide and hydrogen gas. It also reacts with the oxygen and nitrogen in the air to form a mixture of calcium oxide and calcium nitride. When finely divided, it spontaneously burns in air to produce the nitride. In bulk, calcium is less reactive: it quickly forms a hydration coating in moist air, but below 30% relative humidity it may be stored indefinitely at room temperature.

Besides the simple oxide CaO, the peroxide CaO2 can be made by direct oxidation of calcium metal under a high pressure of oxygen, and there is some evidence for a yellow superoxide Ca(O2)2. Calcium hydroxide, Ca(OH)2, is a strong base, though it is not as strong as the hydroxides of strontium, barium or the alkali metals. All four dihalides of calcium are known. Calcium carbonate (CaCO3) and calcium sulfate (CaSO4) are particularly abundant minerals. Like strontium and barium, as well as the alkali metals and the divalent lanthanides europium and ytterbium, calcium metal dissolves directly in liquid ammonia to give a dark blue solution.

Due to the large size of the Ca2+ ion, high coordination numbers are common, up to 24 in some intermetallic compounds such as CaZn13. Calcium is readily complexed by oxygen chelates such as EDTA and polyphosphates, which are useful in analytic chemistry and removing calcium ions from hard water. In the absence of steric hindrance, smaller group 2 cations tend to form stronger complexes, but when large polydentate macrocycles are involved the trend is reversed.

Although calcium is in the same group as magnesium and organomagnesium compounds are very commonly used throughout chemistry, organocalcium compounds are not similarly widespread because they are more difficult to make and more reactive, although they have recently been investigated as possible catalysts. Organocalcium compounds tend to be more similar to organoytterbium compounds due to the similar ionic radii of Yb2+ (102 pm) and Ca2+ (100 pm). Most of these compounds can only be prepared at low temperatures; bulky ligands tend to favor stability. For example, calcium dicyclopentadienyl, Ca(C5H5)2, must be made by directly reacting calcium metal with mercurocene or cyclopentadiene itself; replacing the C5H5 ligand with the bulkier C5(CH3)5 ligand on the other hand increases the compound's solubility, volatility, and kinetic stability.

Isotopes

Natural calcium is a mixture of five stable isotopes (40Ca, 42Ca, 43Ca, 44Ca, and 46Ca) and one isotope with a half-life so long that it can be considered stable for all practical purposes (48Ca, with a half-life of about 4.3 × 1019 years). Calcium is the first (lightest) element to have six naturally occurring isotopes.

By far the most common isotope of calcium in nature is 40Ca, which makes up 96.941% of all natural calcium. It is produced in the silicon-burning process from fusion of alpha particles and is the heaviest stable nuclide with equal proton and neutron numbers; its occurrence is also supplemented slowly by the decay of primordial 40K. Adding another alpha particle would lead to unstable 44Ti, which quickly decays via two successive electron captures to stable 44Ca; this makes up 2.806% of all natural calcium and is the second-most common isotope. The other four natural isotopes, 42Ca, 43Ca, 46Ca, and 48Ca, are significantly rarer, each comprising less than 1% of all natural calcium. The four lighter isotopes are mainly products of the oxygen-burning and silicon-burning processes, leaving the two heavier ones to be produced via neutron-capturing processes. 46Ca is mostly produced in a "hot" s-process, as its formation requires a rather high neutron flux to allow short-lived 45Ca to capture a neutron. 48Ca is produced by electron capture in the r-process in type Ia supernovae, where high neutron excess and low enough entropy ensures its survival.

46Ca and 48Ca are the first "classically stable" nuclides with a six-neutron or eight-neutron excess respectively. Although extremely neutron-rich for such a light element, 48Ca is very stable because it is a doubly magic nucleus, having 20 protons and 28 neutrons arranged in closed shells. Its beta decay to 48Sc is very hindered because of the gross mismatch of nuclear spin: 48Ca has zero nuclear spin, being even–even, while 48Sc has spin 6+, so the decay is forbidden by the conservation of angular momentum. While two excited states of 48Sc are available for decay as well, they are also forbidden due to their high spins. As a result, when 48Ca does decay, it does so by double beta decay to 48Ti instead, being the lightest nuclide known to undergo double beta decay. The heavy isotope 46Ca can also theoretically undergo double beta decay to 46Ti as well, but this has never been observed; the lightest and most common isotope 40Ca is also doubly magic and could undergo double electron capture to 40Ar, but this has likewise never been observed. Calcium is the only element to have two primordial doubly magic isotopes. The experimental lower limits for the half-lives of 40Ca and 46Ca are 5.9 × 1021 years and 2.8 × 1015 years respectively.

Apart from the practically stable 48Ca, the longest lived radioisotope of calcium is 41Ca. It decays by electron capture to stable 41K with a half-life of about a hundred thousand years. Its existence in the early Solar System as an extinct radionuclide has been inferred from excesses of 41K: traces of 41Ca also still exist today, as it is a cosmogenic nuclide, continuously reformed through neutron activation of natural 40Ca. Many other calcium radioisotopes are known, ranging from 34Ca to 57Ca: they are all much shorter-lived than 41Ca, the most stable among them being 45Ca (half-life 163 days) and 47Ca (half-life 4.54 days). The isotopes lighter than 42Ca usually undergo beta plus decay to isotopes of potassium, and those heavier than 44Ca usually undergo beta minus decay to isotopes of scandium, although near the nuclear drip lines proton emission and neutron emission begin to be significant decay modes as well.

Like other elements, a variety of processes alter the relative abundance of calcium isotopes. The best studied of these processes is the mass-dependent fractionation of calcium isotopes that accompanies the precipitation of calcium minerals such as calcite, aragonite and apatite from solution. Lighter isotopes are preferentially incorporated into these minerals, leaving the surrounding solution enriched in heavier isotopes at a magnitude of roughly 0.025% per atomic mass unit (amu) at room temperature. Mass-dependent differences in calcium isotope composition are conventionally expressed by the ratio of two isotopes (usually 44Ca/40Ca) in a sample compared to the same ratio in a standard reference material. 44Ca/40Ca varies by about 1% among common earth materials.

History

One of the 'Ain Ghazal Statues, made from lime plaster
 
Calcium compounds were known for millennia, although their chemical makeup was not understood until the 17th century. Lime as a building material and as plaster for statues was used as far back as around 7000 BC. The first dated lime kiln dates back to 2500 BC and was found in Khafajah, Mesopotamia. At about the same time, dehydrated gypsum (CaSO4·2H2O) was being used in the Great Pyramid of Giza; this material would later be used for the plaster in the tomb of Tutankhamun. The climate of present-day Italy being warmer than that of Egypt, the ancient Romans instead used lime mortars made by heating limestone (CaCO3); the name "calcium" itself derives from the Latin word calx "lime". Vitruvius noted that the lime that resulted was lighter than the original limestone, attributing this to the boiling of the water; in 1755, Joseph Black proved that this was due to the loss of carbon dioxide, which as a gas had not been recognised by the ancient Romans.

In 1787, Antoine Lavoisier suspected that lime might be an oxide of a fundamental chemical element. In his table of the elements, Lavoisier listed five "salifiable earths" (i.e., ores that could be made to react with acids to produce salts (salis = salt, in Latin): chaux (calcium oxide), magnésie (magnesia, magnesium oxide), baryte (barium sulfate), alumine (alumina, aluminium oxide), and silice (silica, silicon dioxide). About these "elements", Lavoisier speculated:
We are probably only acquainted as yet with a part of the metallic substances existing in nature, as all those which have a stronger affinity to oxygen than carbon possesses, are incapable, hitherto, of being reduced to a metallic state, and consequently, being only presented to our observation under the form of oxyds, are confounded with earths. It is extremely probable that barytes, which we have just now arranged with earths, is in this situation; for in many experiments it exhibits properties nearly approaching to those of metallic bodies. It is even possible that all the substances we call earths may be only metallic oxyds, irreducible by any hitherto known process.
Calcium, along with its congeners magnesium, strontium, and barium, was first isolated by Humphry Davy in 1808. Following the work of Jöns Jakob Berzelius and Magnus Martin af Pontin on electrolysis, Davy isolated calcium and magnesium by putting a mixture of the respective metal oxides with mercury(II) oxide on a platinum plate which was used as the anode, the cathode being a platinum wire partially submerged into mercury. Electrolysis then gave calcium–mercury and magnesium–mercury amalgams, and distilling off the mercury gave the metal. However, pure calcium cannot be prepared in bulk by this method and a workable commercial process for its production was not found until over a century later.

Occurrence and production

Travertine terraces in Pamukkale, Turkey
 
At 3%, calcium is the fifth most abundant element in the Earth's crust, and the third most abundant metal behind aluminium and iron. It is also the fourth most abundant element in the lunar highlands. Sedimentary calcium carbonate deposits pervade the Earth's surface as fossilized remains of past marine life; they occur in two forms, the rhombohedral calcite (more common) and the orthorhombic aragonite (forming in more temperate seas). Minerals of the first type include limestone, dolomite, marble, chalk, and iceland spar; aragonite beds make up the Bahamas, the Florida Keys, and the Red Sea basins. Corals, sea shells, and pearls are mostly made up of calcium carbonate. Among the other important minerals of calcium are gypsum (CaSO4·2H2O), anhydrite (CaSO4), fluorite (CaF2), and apatite ([Ca5(PO4)3F]).

The major producers of calcium are China (about 10000 to 12000 tonnes per year), Russia (about 6000 to 8000 tonnes per year), and the United States (about 2000 to 4000 tonnes per year). Canada and France are also among the minor producers. In 2005, about 24000 tonnes of calcium were produced; about half of the world's extracted calcium is used by the United States, with about 80% of the output used each year. In Russia and China, Davy's method of electrolysis is still used, but is instead applied to molten calcium chloride. Since calcium is less reactive than strontium or barium, the oxide–nitride coating that results in air is stable and lathe machining and other standard metallurgical techniques are suitable for calcium. In the United States and Canada, calcium is instead produced by reducing lime with aluminium at high temperatures.

Geochemical cycling

Calcium cycling provides a link between tectonics, climate, and the carbon cycle. In the simplest terms, uplift of mountains exposes calcium-bearing rocks to chemical weathering and releases Ca2+ into surface water. These ions are transported to the ocean where they react with dissolved CO2 to form limestone (CaCO
3
), which in turn settles to the sea floor where it is incorporated into new rocks. Dissolved CO2, along with carbonate and bicarbonate ions, are termed "dissolved inorganic carbon" (DIC).

The actual reaction is more complicated and involves the bicarbonate ion (HCO
3
) that forms when CO2 reacts with water at seawater pH:
Ca2+ + 2HCO
3
CaCO
3
(s) + CO
2
+ H
2
O
At seawater pH, most of the CO2 is immediately converted back into HCO
3
. The reaction results in a net transport of one molecule of CO2 from the ocean/atmosphere into the lithosphere. 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. The weathering of calcium from rocks thus scrubs CO2 from the ocean and atmosphere, exerting a strong long-term effect on climate.

Uses

The largest use of calcium is in steelmaking, due to its strong chemical affinity for oxygen and sulfur. Its oxides and sulfides, once formed, give liquid lime aluminate and sulfide inclusions in steel which float out; on treatment, these inclusions disperse throughout the steel and became small and spherical, improving castability, cleanliness and general mechanical properties. Calcium is also used in maintenance-free automotive batteries, in which the use of 0.1% calcium–lead alloys instead of the usual antimony–lead alloys leads to lower water loss and lower self-discharging. Due to the risk of expansion and cracking, aluminium is sometimes also incorporated into these alloys. These lead–calcium alloys are also used in casting, replacing lead–antimony alloys. Calcium is also used to strengthen aluminium alloys used for bearings, for the control of graphitic carbon in cast iron, and to remove bismuth impurities from lead. Calcium metal is found in some drain cleaners, where it functions to generate heat and calcium hydroxide that saponifies the fats and liquefies the proteins (for example, those in hair) that block drains. Besides metallurgy, the reactivity of calcium is exploited to remove nitrogen from high-purity argon gas and as a getter for oxygen and nitrogen. It is also used as a reducing agent in the production of chromium, zirconium, thorium, and uranium. It can also be used to store hydrogen gas, as it reacts with hydrogen to form solid calcium hydride, from which the hydrogen can easily be re-extracted.

Calcium isotope fractionation during mineral formation has led to several applications of calcium isotopes. In particular, the 1997 observation by Skulan and DePaolo that calcium minerals are isotopically lighter than the solutions from which the minerals precipitate is the basis of analogous applications in medicine and in paleooceanography. In animals with skeletons mineralized with calcium, the calcium isotopic composition of soft tissues reflects the relative rate of formation and dissolution of skeletal mineral. In humans, changes in the calcium isotopic composition of urine have been shown to be related to changes in bone mineral balance. When the rate of bone formation exceeds the rate of bone resorption, the 44Ca/40Ca ratio in soft tissue rises and vice versa. Because of this relationship, calcium isotopic measurements of urine or blood may be useful in the early detection of metabolic bone diseases like osteoporosis. A similar system exists in seawater, where 44Ca/40Ca tends to rise when the rate of removal of Ca2+ by mineral precipitation exceeds the input of new calcium into the ocean. In 1997, Skulan and DePaolo presented the first evidence of change in seawater 44Ca/40Ca over geologic time, along with a theoretical explanation of these changes. More recent papers have confirmed this observation, demonstrating that seawater Ca2+ concentration is not constant, and that the ocean is never in a "steady state" with respect to calcium input and output. This has important climatological implications, as the marine calcium cycle is closely tied to the carbon cycle.

Many calcium compounds are used in food, as pharmaceuticals, and in medicine, among others. For example, calcium and phosphorus are supplemented in foods through the addition of calcium lactate, calcium diphosphate, and tricalcium phosphate. The last is also used as a polishing agent in toothpaste and in antacids. Calcium lactobionate is a white powder that is used as a suspending agent for pharmaceuticals. In baking, calcium monophosphate is used as a leavening agent. Calcium sulfite is used as a bleach in papermaking and as a disinfectant, calcium silicate is used as a reinforcing agent in rubber, and calcium acetate is a component of liming rosin and is used to make metallic soaps and synthetic resins.

Biological and pathological role

Age-adjusted daily calcium recommendations (from U.S. Institute of Medicine RDAs)
Age Calcium (mg/day)
1–3 years 700
4–8 years 1000
9–18 years 1300
19–50 years 1000
>51 years 1000
Pregnancy 1000
Lactation 1000

Global dietary calcium intake among adults (mg/day).
  <400 span="">
  400-500
  500-600
  600-700
  700-800
  800-900
  900-1000
  >1000

Calcium is an essential element needed in large quantities. The Ca2+ ion acts as an electrolyte and is vital to the health of the muscular, circulatory, and digestive systems; is indispensable to the building of bone; and supports synthesis and function of blood cells. For example, it regulates the contraction of muscles, nerve conduction, and the clotting of blood. As a result, intra- and extracellular calcium levels are tightly regulated by the body. Calcium can play this role because the Ca2+ ion forms stable coordination complexes with many organic compounds, especially proteins; it also forms compounds with a wide range of solubilities, enabling the formation of skeletons.

Calcium ions may be complexed by proteins through binding the carboxyl groups of glutamic acid or aspartic acid residues; through interacting with phosphorylated serine, tyrosine, or threonine residues; or by being chelated by γ-carboxylated amino acid residues. Trypsin, a digestive enzyme, uses the first method; osteocalcin, a bone matrix protein, uses the third. Some other bone matrix proteins such as osteopontin and bone sialoprotein use both the first and the second. Direct activation of enzymes by binding calcium is common; some other enzymes are activated by noncovalent association with direct calcium-binding enzymes. Calcium also binds to the phospholipid layer of the cell membrane, anchoring proteins associated with the cell surface. As an example of the wide range of solubility of calcium compounds, monocalcium phosphate is very soluble in water, 85% of extracellular calcium is as dicalcium phosphate with a solubility of 2.0 mM and the hydroxyapatite of bones in an organic matrix is tricalcium phosphate at 100 µM.

About three-quarters of dietary calcium is from dairy products and grains, the rest being accounted for by vegetables, protein-rich foods, fruits, sugar, fats, and oil. Calcium supplementation is controversial, as the bioavailability of calcium is strongly dependent on the solubility of the salt involved: calcium citrate, malate, and lactate are highly bioavailable while the oxalate is much less so. The intestine absorbs about one-third of calcium eaten as the free ion, and plasma calcium level is then regulated by the kidneys. Parathyroid hormone and vitamin D promote the formation of bone by allowing and enhancing the deposition of calcium ions there, allowing rapid bone turnover without affecting bone mass or mineral content. When plasma calcium levels fall, cell surface receptors are activated and the secretion of parathyroid hormone occurs; it then proceeds to stimulate the entry of calcium into the plasma pool by taking it from targeted kidney, gut, and bone cells, with the bone-forming action of parathyroid hormone being antagonised by calcitonin, whose secretion increases with increasing plasma calcium levels.

Excess intake of calcium may cause hypercalcaemia. However, because calcium is absorbed rather inefficiently by the intestines, high serum calcium is more likely caused by excessive secretion of parathyroid hormone (PTH) or possibly by excessive intake of vitamin D, both which facilitate calcium absorption. It may also be due to bone destruction that occurs when tumours metastasize within bone. All these conditions result in excess calcium salts being deposited in the heart, blood vessels, or kidneys. Symptoms include anorexia, nausea, vomiting, memory loss, confusion, muscle weakness, increased urination, dehydration, and metabolic bone disease. Chronic hypercalcaemia typically leads to calcification of soft tissue and its serious consequences: for example, calcification can cause loss of elasticity of vascular walls and disruption of laminar blood flow—and thence to plaque rupture and thrombosis. Conversely, inadequate calcium or vitamin D intakes may result in hypocalcaemia, often caused also by inadequate secretion of parathyroid hormone or defective PTH receptors in cells. Symptoms include neuromuscular excitability, which potentially causes tetany and disruption of conductivity in cardiac tissue.

As calcium is heavily involved in bone manufacture, many bone diseases can be traced to problems with the organic matrix or the hydroxyapatite in molecular structure or organisation. For example, osteoporosis is a reduction in mineral content of bone per unit volume, and can be treated by supplementation of calcium, vitamin D, and biphosphates. Calcium supplements may benefit the serum lipids in women who have passed menopause as well as older men; in post-menopausal women calcium supplementation also appears to be inversely correlated with cardiovascular disease. Inadequate amounts of calcium, vitamin D, or phosphates can lead to the softening of bones, known as osteomalacia.

Safety

Metallic calcium

Calcium
Hazards
GHS pictograms The flame pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)
GHS signal word Danger
H261
P231+232, P422
NFPA 704
Flammability code 3: Liquids and solids that can be ignited under almost all ambient temperature conditions. Flash point between 23 and 38 °C (73 and 100 °F). E.g., gasolineHealth code 0: Exposure under fire conditions would offer no hazard beyond that of ordinary combustible material. E.g., sodium chlorideReactivity code 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g., calciumSpecial hazard W: Reacts with water in an unusual or dangerous manner. E.g., cesium, sodiumNFPA 704 four-colored diamond
3
0
1
W

Because calcium reacts exothermically with water and acids, calcium metal coming into contact with bodily moisture results in severe corrosive irritation. When swallowed, calcium metal has the same effect on the mouth, oesophagus, and stomach, and can be fatal. However, long-term exposure is not known to have distinct adverse effects.

Calcium in food

Because of concerns for long-term adverse side effects, including calcification of arteries and kidney stones, both the U.S. Institute of Medicine (IOM) and the European Food Safety Authority (EFSA) set Tolerable Upper Intake Levels (ULs) for combined dietary and supplemental calcium. From the IOM, people of ages 9–18 years are not to exceed 3 g/day combined intake; for ages 19–50, not to exceed 2.5 g/day; for ages 51 and older, not to exceed 2 g/day. The EFSA set the UL for all adults at 2.5 g/day, but decided the information for children and adolescents was not sufficient to determine ULs.

Liberal Christianity

From Wikipedia, the free encyclopedia

Liberal Christianity, also known as liberal theology, covers diverse philosophically and biblically informed religious movements and ideas within Christianity from the late 18th century onward. Liberal does not refer to progressive Christianity or to political liberalism but to the philosophical and religious thought that developed and grew as a consequence of the Enlightenment.
 
Liberal Christianity, broadly speaking, is a method of biblical hermeneutics, an undogmatic method of understanding God through the use of scripture by applying the same modern hermeneutics used to understand any ancient writings, symbols and scriptures. Liberal Christianity did not originate as a belief structure, and as such was not dependent upon any Church dogma or creed. Liberal Christianity from the start embraced the methodologies of Enlightenment science, including empirical evidence and the use of reason, as the basis for interpreting the Bible, life, faith and theology.

The word liberal in liberal Christianity originally denoted a characteristic willingness to interpret scripture according to modern philosophic perspectives (hence the parallel term modernism) and modern scientific assumptions, while attempting to achieve the Enlightenment ideal of objective point of view, without preconceived notions of the authority of scripture or the correctness of Church dogma. Liberal Christians may hold certain beliefs in common with Roman Catholicism, Orthodox Christianity, or even fundamentalist Protestantism.

Liberal Protestantism

Liberal Protestantism developed in the 19th century out of a need to adapt Christianity to a modern intellectual context. With the acceptance of Charles Darwin's theory of natural selection, some traditional Christian beliefs, such as parts of the Genesis creation narrative, became difficult to defend. Unable to ground faith exclusively in an appeal to scripture or the person of Jesus Christ, liberals, according to theologian and intellectual historian Alister McGrath, "sought to anchor that faith in common human experience, and interpret it in ways that made sense within the modern worldview." Beginning in Germany, liberal theology was influenced by several strands of thought, including the Enlightenment's high view of human reason and Pietism's emphasis on religious experience and interdenominational tolerance.

The sources of religious authority recognized by liberal Protestants differed from traditional Protestants. Traditional Protestants understood the Bible to be uniquely authoritative (sola scriptura); all doctrine, teaching and the church itself derive authority from it. A traditional Protestant could therefore affirm that "what Scripture says, God says." Liberals, however, seek to understand the Bible through modern biblical criticism, such as historical criticism, that began to be used in the late 1700s to ask if biblical accounts were based on older texts or whether the Gospels recorded the actual words of Jesus. The use of these methods of biblical interpretation led liberals to conclude that "none of the New Testament writings can be said to be apostolic in the sense in which it has been traditionally held to be so". This conclusion made sola scriptura untenable. In its place, liberals identified the historical Jesus as the "real canon of the Christian church".

The two groups also disagreed on the role of experience in confirming truth claims. Traditional Protestants believed scripture and revelation always confirmed human experience and reason. For liberal Protestants , there were two ultimate sources of religious authority: the Christian experience of God as revealed in Jesus Christ and universal human experience. In other words, only an appeal to common human reason and experience could confirm the truth claims of Christianity.

Liberals abandoned or reinterpreted traditional doctrines in light of recent knowledge. For example, the traditional doctrine of original sin was rejected for being derived from Augustine of Hippo, whose views on the New Testament were believed to have been distorted by his involvement with Manichaeism. Christology was also reinterpreted. Liberals stressed Christ's humanity, and his divinity became "an affirmation of Jesus exemplifying qualities which humanity as a whole could hope to emulate". Liberal Christians sought to elevate Jesus' humane teachings as a standard for a world civilization freed from cultic traditions and traces of "pagan" belief in the supernatural.

As a result, liberal Christians placed less emphasis on miraculous events associated with the life of Jesus than on his teachings. The effort to remove "superstitious" elements from Christian faith dates to intellectually reforming Renaissance Christians such as Erasmus (who compiled the first modern Greek New Testament) in the late 15th and early-to-mid 16th centuries, and, later, the natural-religion view of the Deists, which disavowed any revealed religion or interaction between the Creator and the creation, in the 17–18th centuries. The debate over whether a belief in miracles was mere superstition or essential to accepting the divinity of Christ constituted a crisis within the 19th-century church, for which theological compromises were sought. Many liberals prefer to read Jesus' miracles as metaphorical narratives for understanding the power of God. Not all theologians with liberal inclinations reject the possibility of miracles, but many reject the polemicism that denial or affirmation entails.

Nineteenth-century liberalism had an optimism about the future in which humanity would continue to achieve greater progress. This optimistic view of history was sometimes interpreted as building the kingdom of God in the world.

Theologians

Reformed theologian Friedrich Schleiermacher is often considered the father of liberal Protestantism. In response to Romanticism's disillusionment with Enlightenment rationalism, Schleiermacher argued that God could only be experienced through feeling, not reason. In Schleiermacher's theology, religion is a feeling of absolute dependence on God. Humanity is conscious of its own sin and its need of redemption, which can only be accomplished by Jesus Christ. For Schleirmacher, faith is experienced within a faith community, never in isolation. This meant that theology always reflects a particular religious context, which has opened Schleirmacher to charges of relativism.

Albrecht Ritschl disagreed with Schleiermacher's emphasis on feeling. He thought that religious belief should be based on history, specifically the historical events of the New Testament. When studied as history without regard to miraculous events, Ritschl believed the New Testament affirmed Jesus' divine mission. He rejected doctrines such as the virgin birth of Jesus and the Trinity. The Christian life for Ritschl was devoted to ethical activity and development, so he understood doctrines to be value judgments rather than assertions of facts. Influenced by the philosophy of Emmanuel Kant, Ritschl viewed "religion as the triumph of the spirit (or moral agent) over humanity’s natural origins and environment." Ritschl's ideas would be taken up by others, and Ritschlianism would remain an important theological school within German Protestantism until World War I. Prominent followers of Ritschl include Wilhelm Herrmann, Julius Kaftan and Adolf von Harnack.

Liberal Catholicism

Catholic forms of theological liberalism have existed since the 19th century in England, France and Italy. In the late 19th and early 20th centuries, a liberal theological movement developed within the Catholic Church known as Catholic modernism. Like liberal Protestantism, Catholic modernism was an attempt to bring Catholicism in line with the Enlightenment. Modernist theologians approved of radical biblical criticism and were willing to question traditional Christian doctrines, especially Christology. They also emphasized the ethical aspects of Christianity over its theological ones. Important modernist writers include Alfred Loisy and George Tyrrell. Modernism was condemned as heretical by the leadership of the Catholic Church.

Papal condemnation of modernism and Americanism slowed the development of a liberal Catholic tradition in the United States. Since the Second Vatican Council, however, liberal theology has experienced a resurgence. Liberal Catholic theologians include David Tracy and Francis Schussler Fiorenza.

Influence in the United States

Liberal Christianity was most influential with Mainline Protestant churches in the early 20th century, when proponents believed the changes it would bring would be the future of the Christian church. Its greatest and most influential manifestation was the Christian Social Gospel, whose most influential spokesman was the American Baptist Walter Rauschenbusch. Rauschenbusch identified four institutionalized spiritual evils in American culture (which he identified as traits of "supra-personal entities", organizations capable of having moral agency): these were individualism, capitalism, nationalism and militarism.

Other subsequent theological movements within the U.S. Protestant mainline included political liberation theology, philosophical forms of postmodern Christianity, and such diverse theological influences as Christian existentialism (originating with Søren Kierkegaard and including other theologians and scholars such as Rudolf Bultmann and Paul Tillich ) and even conservative movements such as neo-evangelicalism, neo-orthodoxy, and paleo-orthodoxy. Dean M. Kelley, a liberal sociologist, was commissioned in the early 1970s to study the problem, and he identified a potential reason for the decline of the liberal churches: what was seen by some as excessive politicization of the Gospel, and especially their apparent tying of the Gospel with Left-Democrat/progressive political causes.

The 1990s and 2000s saw a resurgence of non-doctrinal, theological work on biblical exegesis and theology, exemplified by figures such as Marcus Borg, John Dominic Crossan, John Shelby Spong, Karen Armstrong and Scotty McLennan.

Theologians and authors

Anglican and Protestant

Roman Catholic

Other

Bible Belt

From Wikipedia, the free encyclopedia

The area roughly considered to constitute the Bible Belt
 
The Bible Belt is an informal region in the Southern United States in which socially conservative evangelical Protestantism plays a strong role in society and politics, and Christian church attendance across the denominations is generally higher than the nation's average.

The region is usually contrasted with the religiously diverse Midwest and Great Lakes, the Mormon Corridor in Utah and southern Idaho, and the relatively secular Western and New England regions of the United States. Whereas the state with the highest percentage of residents identifying as non-religious is the New England state of Vermont at 37%, in the Bible Belt state of Alabama it is just 12%. Tennessee has the highest proportion of Evangelical Protestants, at 52%. The Evangelical influence is strongest in northern Georgia, Tennessee, Alabama, Mississippi, North Carolina, southern Virginia, South Carolina, and eastern Texas. The earliest known usage of the term "Bible Belt" was by American journalist and social commentator H. L. Mencken, who in 1924 wrote in the Chicago Daily Tribune: "The old game, I suspect, is beginning to play out in the Bible Belt." In 1927, Mencken claimed the term as his invention.

Geography

The name "Bible Belt" has been applied historically to the South and parts of the Midwest, but is more commonly identified with the South. In a 1961 study, Wilbur Zelinsky delineated the region as the area in which Protestant denominations, especially Southern Baptist, Methodist, and evangelical, are the predominant religious affiliation. The region thus defined included most of the Southern United States, including most of Texas and Oklahoma, and in the states south of the Ohio River, and extending east to include central West Virginia and Virginia, from the Shenandoah Valley southward. In addition, the Bible Belt covers most of Missouri and Kentucky and southern parts of Illinois, Indiana, and Ohio. On the other hand, areas in the South which are not considered part of the Bible Belt include heavily Catholic Southern Louisiana, central and southern Florida, which have been settled mainly by immigrants and Americans from elsewhere in the country, and overwhelmingly Hispanic South Texas. A 1978 study by Charles Heatwole identified the Bible Belt as the region dominated by 24 fundamentalist Protestant denominations, corresponding to essentially the same area mapped by Zelinsky.

According to Stephen W. Tweedie, an Associate Professor Emeritus in the Department of Geography at Oklahoma State University, the Bible Belt is now viewed in terms of numerical concentration of the audience for religious television. He finds two belts: one more eastern that stretches from Florida, (excluding Miami, Tampa and South Florida), through Alabama, Tennessee, Kentucky, Georgia, North and South Carolina, and into Southern Virginia ; and another concentrated in Texas (excluding El Paso, and South Texas), Arkansas, Louisiana, (excluding New Orleans and Acadiana), Oklahoma, Missouri (excluding St. Louis), Kansas, and Mississippi. "[H]is research also broke the Bible Belt into two core regions, a western region and an eastern region. Tweedie's western Bible Belt was focused on a core that extended from Little Rock, Arkansas to Tulsa, Oklahoma. His eastern Bible Belt was focused on a core that included the major population centers of Virginia and North Carolina.

Bible-minded cities map
 
A study was commissioned by the American Bible Society to survey the importance of the Bible in the metropolitan areas of the United States. The report was based on 42,855 interviews conducted between 2005 and 2012. It determined the 10 most "Bible-minded" cities were Knoxville, Tennessee; Shreveport, Louisiana; Chattanooga, Tennessee; Birmingham, Alabama; Jackson, Mississippi; Springfield, Missouri; Charlotte, North Carolina;, Lynchburg, Virginia; Huntsville-Decatur, Alabama; and Charleston, West Virginia.

In addition to the South, there is a smaller Bible Belt in West Michigan, centered around the heavily Dutch-influenced cities of Holland and Grand Rapids. Christian colleges in that region include Calvin College, Hope College, Cornerstone University, Grace Bible College, and Kuyper College. West Michigan is generally fiscally and socially conservative.

History

During the colonial period (1607–1776), the South was a stronghold of the Anglican church. Its transition to a stronghold of non-Anglican Protestantism occurred gradually over the next century as a series of religious revival movements, many associated with the Baptist denomination, gained great popularity in the region.

It seems a link between the colonial Bible Belt (the North, especially New England with its Puritan heritage) and the later Southern Bible Belt may be seen in the impact which some Northern figures had on the religious development of the South (perhaps not incomparable to the origins of Mormonism in the North, in spite of its later association with Utah). "The centre of Particular Baptist activity in early America was in the Middle Colonies. In 1707 five churches in New Jersey, Pennsylvania, and Delaware were united to form the Philadelphia Baptist Association, and through the association they embarked upon vigorous missionary activity. By 1760 the Philadelphia association included churches located in the present states of Connecticut, New York, New Jersey, Pennsylvania, Delaware, Virginia, and West Virginia; and by 1767 further multiplication of churches had necessitated the formation of two subsidiary associations, the Warren in New England and the Ketochton in Virginia. The Philadelphia association also provided leadership in organizing the Charleston Association in the Carolinas in 1751." An influential figure was Shubal Stearns: "Shubael Stearns, a New England Separate Baptist, migrated to Sandy Creek, North Carolina, in 1755 and initiated a revival that quickly penetrated the entire Piedmont region. The churches he organized were brought together in 1758 to form the Sandy Creek Association". Stearns was brother-in-law of Daniel Marshall, who was born in Windsor, Connecticut and "is generally considered the first great Baptist leader in Georgia. He founded Kiokee Baptist Church, the oldest continuing Baptist congregation in the state". Also, Wait Palmer, of Toland, Connecticut, may have influenced African American Christianity in the South: "The Silver Bluff, South Carolina, revival was a seminal development, whose role among blacks rivalled that played by the Sandy Creek revival of the Separate Baptists, to which it was indirectly related. It was probably the same Wait Palmer who had baptized Shubal Stearns in 1751 who came to Silver Bluff in 1775, baptizing and constituting a church. Abraham Marshall, who encouraged the later offshoots, was a Separate Baptist of the Sandy Creek school. The revival at the Silver Bluff plantation of George Galphin (some twelve miles from Augusta, Georgia) had brought David George to the Afro-Baptist faith and had provided a ministry for George Liele". According to Thomas S. Kidd, "As early as 1758, Sandy Creek missionaries helped organize a slave congregation, the Bluestone Church, on the plantation of William Byrd III, which may have been the first independently functioning African American church in North America. The church did not last long, but it reflected the Baptists' commitment to evangelizing African Americans". And according to Gayraud S. Wilmore, "The preaching of New England Congregationalists such as Jonathan Edwards about the coming millennium, and his conviction that Christians were called to prepare for it, reached the slaves through the far-ranging missionary work of white evangelists such as Shubal Stearns, Wait Palmer, and Matthew Moore - all of whom left Congregationalism and became Separatist Baptist preachers in the plantation country of Virginia, North and South Carolina, and Georgia".

Buckle

A billboard near the center of Alabama

Several locations are occasionally referred to as "the Buckle of the Bible Belt":

Political and cultural context

There has been research that links evangelical Protestantism with social conservatism. In 1950, President Harry S. Truman told Catholic leaders he wanted to send an ambassador to the Vatican. Truman said the leading Democrats in Congress approved, but they warned him, "it would defeat Democratic Senators and Congressmen in the Bible Belt."

In presidential elections, the Bible Belt states of Alabama, Mississippi, South Carolina, and Texas have voted for the Republican candidate in all elections since 1980; Oklahoma has supported the Republican presidential candidate in every election since 1968. Other Bible Belt states have voted for the Republican presidential candidate in the majority of elections since 1980, but have gone to the Democratic candidate either once or twice since then. However, with the exception of Mississippi, historical geographer Barry Vann shows that counties in the upland areas of the Appalachians and the Ozarks have a more conservative voting pattern than the counties located in the coastal plains.

Outside the United States

Australia

In Australia, the term "Bible Belt" has been used to refer to areas within individual cities, which have a high concentration of Christians, usually centralised around a megachurch, for example:
Toowoomba city in Queensland has long been regarded as fertile ground for Christian fundamentalist right-wing movements  that adhere to biblical literalism, particularly those within the Pentecostal and charismatic stream of Christianity. This was exemplified by the highly publicised rise and subsequent fall of Howard Carter and the Logos Foundation in the 1980s. The Logos Foundation and other similar movements that have followed it, operate in a controlling, authoritarian and almost cultish manner, contributing to their notoriety. Other similarly conservative Pentecostal churches within the city have, since that time, banded together into a loose federation known as the Toowoomba Christian Leaders' Network. (note - most traditional church denominations have their own, separate ecumenical group) This network views itself as having a divine mission to 'take the city for the Lord' and as such, endorses elements of religious right-wing political advocacy, such as the Australian Christian Lobby(ACL). ACL's former managing director who was raised in the Logos Foundation and is a former Toowoomba City councillor is Lyle Shelton. These church groups are strongly associated with North American trends such as the New Apostolic Reformation, Dominion theology, Five-fold ministry thinking, Kingdom Now theology and revivalism. They support the achievement of a type of theocratic society where conservative and literal interpretations of the bible are the dominant drivers of government, education, the Arts, the media and entertainment. Churches involved in this group currently include the successor organization to the Logos Foundation, the Toowoomba City Church, along with the Range Christian Fellowship, Spring Street Assembly of God, Christian Outreach Centre, Hume Ridge Church of Christ, Revival Ministries of Australia Shiloh Centre, the Edge Christian Centre and many others.

Canada

The province of Saskatchewan has been referred to as Canada's Bible Belt with a significant Catholic, Anabaptist population and other Protestants.

Estonia

Census results show religious belief in the country is more prevalent in the east running from north to south along the border with Russia, particularly in those areas with large populations of Russian Orthodox, Estonian Orthodox and Orthodox Old Believers.

Finland

Conservative Laestadianism, a Finnish Lutheran revival, is widespread in northern (Northern Ostrobothnia and Lapland (Finland)) and central parts (Northern Savonia) of Finland.

Germany

Rural portions of Bavaria, approximately stretching from Franconia into Württemberg, constitute Germany's Bible Belt with mostly Catholics, some Lutherans and Reformed Protestants. An area in Erzgebirge in Saxony has been described also as the "Saxon Bible Belt" with a notable evangelical Protestant/Christian fundamentalist/free church community, as well as some conservative Lutheran parishes that are opposed to homosexual marriage. Nevertheless, the Evangelical-Lutheran Church of Saxony approved church resolutions regarding the issue regardless of opinions within those parishes.

Norway

The Bible Belt of Norway is located mainly in the western part of the country and contains numerous devout Lutherans.

Netherlands

The Bible Belt of the Netherlands stretches from Zeeland, through the West-Betuwe and Veluwe, to the northern parts of the province Overijssel. In this region, orthodox Calvinists prevail.

New Zealand

In New Zealand, Mount Roskill, Auckland, contains the highest number of churches per capita in the country, and is the home of several Christian political candidates. The electorate was one of the last in the country to go "wet", in 1999, having formerly been a dry area where the selling of alcohol was prohibited.

At the 2013 New Zealand census, the Mangere–Otahuhu local board area of Auckland had the highest concentration of Christians in New Zealand, with 67.7 percent of the local board's 71,000 residents identifying as such.

Poland

South and East parts of Poland are much more religious than North and West.

Slovakia

In the eastern and northern parts of Slovakia, Christians comprise a majority, in some towns and villages almost 100%.

Soviet Union

Before its independence, Soviet Ukraine was known as the Bible Belt of the Soviet Union with a significant proportion of Baptists.

Sweden

The area normally called the Bible Belt of Sweden is centered on Jönköping in southern Sweden and contains numerous free churches. There are also numerous conservative Lutheran Laestadians in the Torne valley area in the far north of the country.

United Kingdom and Ireland

In Northern Ireland, the area in County Antrim stretching from roughly Ballymoney to Larne and centred in the area of Ballymena is often referred to as a Bible Belt. This is because the area is heavily Protestant with a large evangelical community. From 1970 to 2010, the MP for North Antrim was Ian Paisley, a Free Presbyterian minister well known for his theological fundamentalism. The town of Ballymena, the largest town in the constituency, is often referred to as the "buckle" of the Bible Belt. In the Republic of Ireland, County Wicklow and western parts of County Cork have the highest population of Protestants.

Introduction to entropy

From Wikipedia, the free encyclopedia https://en.wikipedia.org/wiki/Introduct...