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Calcium is a metallic element, atomic number 20, symbol Ca, in the periodic table of the elements in the fourth period, group IIA. Calcium is a silver-white solid at room temperature and has active chemical properties. Therefore, it exists in the form of ion or compound in nature.
Chemical property
Most non-metals react directly with heating, such as with sulfur, nitrogen, carbon, hydrogen reaction to calcium sulfide CaS, calcium nitride Ca3N2, calcium carbide CaC2 and calcium hydrogen CaH2, heating reaction with carbon dioxide. [1]
Active chemical properties, in the air surface can form a layer of oxide or nitride film, can slow further corrosion. It can be combined with oxidation to produce calcium oxide, combined with nitrogen to produce calcium nitride Ca3N2, combined with fluorine, chlorine, bromine, iodine, etc., to produce the corresponding halide, and hydrogen under the action of 400ºC catalyst to produce calcium hydride. At room temperature, it reacts with water to produce calcium hydroxide and give off hydrogen, reacts with hydrochloric acid, dilute sulfuric acid and so on to produce salt and hydrogen, and reacts with carbon at high temperature to produce calcium carbide CaC2. Almost all metal oxides can be reduced by heating, and many metal chlorides can be reduced by melting.
Compounds: The important compounds of calcium are calcium hydroxide, calcium oxide, calcium peroxide, calcium chloride, calcium fluoride, calcium carbide, calcium hydroxide, calcium cyanamide, calcium carbonate, calcium hypochlorite, calcium sulfate, etc. Calcium reacts with liquid ammonia to form Ca (NH3) 6, which is a conductive solid with metallic luster. Calcium ions can form chelate [CaEDTA]2 (EDTA is ethylenediamine tetraacetic acid). Calcium ions can form complexes with compounds containing N and O coordination atoms, and form macrocyclic complexes with crown ether and hole ether. Calcium fluoride CaF2 is a white crystal or powder with a density of 3.18g/cm3, a melting point of 1418ºC and a boiling point of 2533.4ºC. It is insoluble in water and dissolves in strong inorganic acid to release hydrogen fluoride. The natural calcium fluoride mineral is fluorite or fluorspar, often gray, yellow, green, purple and other colors. Calcium fluoride is commonly prepared by neutralizing calcium hydroxide with in industry.Calcium fluoride can also be prepared by absorbing waste gas from the production of calcium magnesium phosphate fertilizer with water and neutralizing it with lime milk. Calcium peroxide CaO2 is a yellow-white crystal belonging to tetragonal system with a density of 2.9g/cm3. It explodes when heated to 275ºC. Easy deliquescence, slightly soluble in water, react with dilute sulfuric acid to produce hydrogen peroxide. Adding hydrogen peroxide and ammonia water to calcium chloride aqueous solution, or calcium hydroxide and ammonium chloride dissolved in water, then adding hydrogen peroxide, both reactions are carried out at about 0ºC, and CaO2·8H2O crystal is precipitated, dehydration and drying at 150 ~ 200ºC, anhydrous calcium peroxide can be obtained. [1]
At room temperature, it reacts violently with water to form calcium hydroxide (lime) and hydrogen.
Ca+2H2O=Ca (OH) 2+H2↑
Dissolved in acid, it can decompose water and release hydrogen.
Electronic arrangement: 1s22s22p63s23p64s2
The chemical equation for calcium:
Ca+2HCl=CaCl2+H2↑
N2+3Ca=Ca3N2 (Combination reaction)
3C+CaO=CaC2+CO↑ (REDOX reaction)
CO2+Ca (OH) 2 (excess) =CaCO3↓+H2O (double decomposition reaction)
2CO2 (excess) +Ca (OH) 2=Ca (HCO3) 2 (combination reaction)
SO2+Ca (OH) 2=CaSO3↓+H2O (double decomposition reaction)
SO3+Ca (OH) 2=CaSO4+H2O
2HNO3+CaCO3=Ca (NO3) 2+H2O+CO2↑ (double decomposition reaction)
2Cl2+2Ca (OH) 2=CaCl2+Ca (ClO) 2+2H2O (REDOX reaction)
CaH2+2H2O=Ca (OH) 2+2H2↑ (REDOX reaction)
2HF+CaCl2=CaF2+2HCl (double decomposition reaction)
SiO2+CaO=CaSiO3 (Combination reaction)
(double decomposition reaction)
(decomposition reaction)
(decomposition reaction)
Proton number
20
Neutron number
20
Atomic number
20
Nuclear charge
20
Owning period
3
Family number
IIA
Electron shell distribution
The 2-8-8-2
Electron shell
K-L-M-N
Preparation method edit broadcast
Calcium chloride is obtained by the reaction of limestone with hydrochloric acid:
CaCO3 + 2 HCL = write CaCl2 + H2O + CO2
1. Electrolysis puts the dry anhydrous calcium chloride into the electrolytic cell, melts the raw material beside the anode (graphite) in the electrolytic cell with oxyacetylene flame spray, that is, opens the cooling water, puts down the cathode (round steel), contacts the surface of the material liquid, and passes the current. Make the molten liquid flow to the cathode to open the circuit.To be most of the raw material after melting continue to add new material, until from the groove along 2 ~ 3cm, the temperature is normal. The calcium metal is deposited on the cathode at a current of 350 to 450A and a voltage of 20 to 25V. The current should be reduced by 50 to 100A before striking the calcium metal deposited on the cathode. After the metal calcium to be knocked down is put into the oil, the cathode contacts the electrolyte level again, and the current is increased by 50 ~ 100A. In order to maintain the temperature of the electrolytic cell, it should be added successively. The chlorine gas escapes from the anode and is recycled.
(Calcium and by-product chlorine gas.)
2. Calcium can be obtained by electrolysis and thermite reduction. Electrolyzed molten salt of calcium chloride, the purity of the product is only 90%. Thermal reduction is the reduction of calcium oxide with aluminum at high temperature, the product purity is higher (99%). Its technological process is relatively simple, is adopted in recent years. Firstly, CaO is prepared by roasting CaCO3. Aluminum is best in small particles or flakes. The molar ratio of calcium oxide to aluminum is 3∶2. The ingredients are mixed to produce the billet. The pressure of the manual oil press may be lower than that of the magnesium silicon billet.
3 metal calcium can be used in 780 ~ 800ºC electrolysis molten calcium chloride. The electrolytic cell can be a graphite crucible, the anode is graphite, and the cathode is iron rod or graphite rod. The current density of the cathode is maintained at 100A/cm2. With the precipitation of calcium metal, the cathode is gradually raised. The calcium metal is covered by a layer of molten calcium chloride that has solidified in the air to prevent oxidation. The purity of calcium is 98% ~ 99%, and the impurities are iron, silicon, aluminum, trace carbon and some chlorine.
Application field editor broadcast
Industrial field
Used for alloy with aluminum, copper, lead, also used for reducing agent to make beryllium, alloy deoxidizer, fat dehydrogenation, etc.
Used as alloy deoxidizing agent, oil dehydrating agent, metallurgical reducing agent, iron and iron alloy desulfurization and decarburizing agent and vacuum tube getter.
Biological field
Calcium is used as a high temperature reducing agent to produce metals chromium, thorium, uranium, rare earth elements, zirconium from oxides and halides, as well as magnetic materials samarium cobalt alloy, hydrogen absorbing materials lanthanum nickel alloy and titanium nickel alloy, etc. The addition of Ca-Si alloys to steel prevents the formation of carbides. Lead calcium alloy containing 0.04% calcium has higher hardness and corrosion resistance, used as cable skin and battery lead plate; The plasticity of aluminum alloy can be enhanced by adding calcium. Calcium is also used as a deoxidizing agent for smelting tin bronze, nickel, steel, vacuum tube and television picture tube in deoxidizing agent, organic solvent dehydrating agent, petroleum refining desulfurizing agent, pure inert gas (such as helium) denitrification agent, decomposition of smelly thiophene and mercaptan. Calcium fluoride is used as a raw material for optical glass, optical fiber, enamel, and as a flux. Calcium peroxide is a mild oxidant used as a bactericidal, antiseptic, bleaching agent and a quick-drying agent for sealing cement.
Human:
Calcium is an essential element for life. In the human body, Ca2+ -binding proteins are found in muscles, nerves, fluids, and bones. Calcium is the main inorganic component of human bones and teeth, and is essential for neurotransmission, muscle contraction, blood clotting, hormone release, and milk secretion. Calcium makes up about 1.4% of the body mass and is involved in metabolism. Insufficient or excess calcium in the human body can affect growth, development and health. [1]
Calcium is the most inorganic salt component in the human body. The total amount of calcium in healthy adults is about 1000 ~ 1300 grams, accounting for about 1.5% ~ 2.0% of body weight. 99% of calcium is found in bones and teeth in the form of bone salts. The rest is found in soft tissues. Calcium in the extracellular fluid accounts for only 0.1% of the total calcium. Bone is the main place where calcium is deposited, so it is called "calcium reservoir". Bone calcium mainly exists in the form of amorphous calcium hydrogen phosphate (CaHPO4) and crystalline hydroxyapatite (3Ca3PO4×Ca (OH) 2), and its composition and physicochemical properties change constantly with the physiological or pathological conditions of human body. There is more calcium hydrogen phosphate in new bone than in old bone, which is gradually converted to hydroxyapatite during bone maturation. Bone maintains a dynamic balance between bone calcium and blood calcium through continuous osteogenesis and bone lysis. [1]
Under normal circumstances, the calcium in the blood is almost all in the plasma, under the action of various calcium regulating hormones blood calcium is relatively constant, 2.25 ~ 2.75mmol/L, slightly higher in children, often at the upper limit. Calcium is present in plasma and extracellular fluid in the following ways: (1) protein-bound calcium. About 40% of total blood calcium. (2) diffusible binding calcium. Calcium bound to organic acids, such as calcium citrate, calcium lactate, calcium phosphate, etc. can be diffused through biofilms, accounting for about 13%. (3) serum free calcium. Ionic calcium (Ca) is in constant exchange with the two types of calcium and is in dynamic equilibrium, and its content is related to blood pH. pH decreases, [Ca] increases, pH increases, and ionic calcium decreases. In the normal pH range, ionic calcium accounts for about 47%. Among the three types of blood calcium, only ionic calcium plays a direct physiological role. Hormones are also regulated in response to ionic calcium and are regulated by the feedback of ionic calcium levels.
Intracellular Ca2 + concentration is much lower than extracellular Ca2 + concentration, which is the reservoir of intracellular Ca2 +. About 80% of calcium is stored in organelles (such as mitochondria, sarcoplasmic reticulum, endoplasmic reticulum, etc.). Calcium in different organelles does not diffuse freely with each other. 10% ~ 20% of calcium is distributed in the cytoplasm and binds with soluble proteins and membrane surface, while free calcium only accounts for 0.1%. [1]
Biological calcium:
The so-called biological calcium is to use mature freshwater pearl mussel shell as raw material. After cleaning impurities, grinding with grinding wheel or soaking with NaOH solution to remove the black skin on the outer surface of mussel shell, adding 3%-5% concentration of alcohol into the fine powder of dried, crushed and sucked mussel shell to boil and disinfected, dried, then crushed and screened so that the fine powder particles are less than 200 mesh to obtain white natural biological calcium powder. The natural biological calcium powder produced by this method contains about 45% calcium, and has a variety of amino acids. It is non-toxic and hormone-free. It can be used as calcium additives in drinks and foods and is easy to be absorbed by the human body.
organization.
Molecular formula
CA
Molecular weight
40.08
alias
calcium
Calcium (powder)
Molecular structure formula
Calcium metal
character
Silvery white soft metal. Soluble in acid, liquid ammonia, slightly soluble in alcohol, insoluble in benzene.
Melting point 850 °C(lit.)
Boiling point 1484 °C(lit.)
Density 1.54g /mL at 25 °C(lit.)
Quality standard
99% :
Appearance: Silver/Gray/Gold Granules
Content Assay(Complexometric EDTA) 98.5-101.5%
99.5% metals basis:
The Appearance shiny silver pieces
X-Ray Diffraction analysis X-ray Diffraction Conforms to Structure
Purity ≥99.5% Based on Trace Metals Impurities of ICP
ICP Assay Confirms calcium component
Trace metal analysis total metallic impurity ≤6000ppm by ICP Atomic emission
99.98% metals basis:
The Appearance is Silver Pieces
X-Ray Diffraction analysis X-ray Diffraction Conforms to Structure
Purity ≥99.98% Based on Trace Metals Impurities of ICP
ICP: Confirms Calcium Component Confirmed
Trace metal analysis total metallic impurity ≤200ppm by ICP Atomic emission
(K, Sc, Mg, Cu, Sr, Ag, Ba, Zn, Ga, Si, Mn, As, Fe, Co)
use
Uses as alloy deoxidizer, oil dehydrant, smelting reducing agent, iron and iron alloy decarburizing agent, also used in pharmaceutical industry
Widely used in metallurgy, chemical, pharmaceutical, electrical and other industries, iron and steel smelting can be used as deoxidation and dephosphorization agent, non-ferrous smelting is an excellent reducing agent
Hazardous nature
Class of inflammable articles in contact with water
Dangerous goods mark F
Danger class code 15
Safety Note 8-24/25-43
* Dangerous characteristics Hydrogen explosion in contact with water
Flammability hazard characteristics flammable in contact with water; Contact with water, acid to produce flammable hydrogen; Hydrolysis to caustic lime milk
Storage and transportation characteristics warehouse ventilation low temperature dry; Store separately from acids and halogenated hydrocarbons
Fire extinguishing agent dry powder, dry sand, dry stone powder
Store sealed and dry.
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