Ø CCHARASTHERISTIC OF HIDROGEN
The chemical name for the element with the symbol H is Hydrogen. The name given by Lavoiser hydrogen in 1783 and derived from the Greek "hydro" which airtinya water and "Genes", which means forming or generating. So the mean hydrogen-forming elements that produce water or water.
Hydrogen is the lightest element contained in the periodic table and is the most numerous element in the universe with the percentage content of hydrogen in the universe is 75% by weight or 93% mol. Hydrogen contained in the earth until the room space as a constituent stars. Hydrogen in the form of elements form diatomic gas (H2), H2 is the lightest gas, colorless, and odorless, and this gas is flammable in the presence of oxygen. Hydrogen gas in the wild there are two molecular forms of orthohidrogen and parahydrogen, the two molecular forms differ in terms of relative electron spin and the nucleus. In ortohidrogen spin two protons are parallel to form a state olekular-called "triplet with spin quantum number 1 (1 / 2 +1 / 2), in parahydrogen, the spins protonya antiparallel to form a state of" singlet "and its spin quantum number 0 (1 / 2-1/2). At STP (Standard Temperature Pressure) hydrogen gas is composed of 25% and 75% of the ortho form. Bentu ortho can not be purified, due to differences in the two forms of hydrogen are the physical properties of both is also different.
Hydrogen has atom1 number and mass number of 1.008. With atomic number is the Hydrogen has a 1s1 electron configuration and atomic number of electrons in the skin 1. Hydrogen is placed at the top along with class 1A, but keep in mind that hydrogen is not a member of the group 1A and hydrogen are not members of any group in the periodic table. Hydrogen is placed in period 1 along with helium, and the block where the hydrogen is in the periodic system is on the block s.
Hydrogen has 3 isotopes of the wild 1H, 2H, and 3H. 1H is a hydrogen isotope with an abundance of abundant where their abundance is 99.98%. Due to this isotope has 1 proton and 1 electron, the other name is protium. Another stable isotope is 2H known as deuterium and essentially consists of 1 proton and 1 neutron. Deuterium is not radioactive and harmless. These isotopes are used as a marker in the synthesis of organic compounds. Deuterium in the form of 2H2O is often also used as a coolant in nuclear reactors and is also used for fusion reactions. 3H isotope called Tritium contains 2 neutrons and 1 proton in its core and is radioactive and decays into Helium-3 by emitting beta rays. Many are used as tracers in the field of geochemistry and also as a marker in chemistry and biology experiments.
Physical And Chemical Hydrogen
Nature Physics
• melting point : -259.140 C
• Boiling Point : -252.87 0C
• Color : colorless
• Odor : odorless
• Density : 0.08988 g/cm3 at 293 K
• heat capacity : 14.304 J / GK
Chemical Properties
• Heat fusion : 0.117 kJ / mol H2
• Ionization energy 1 : 1312 kJmol
• Electron affinity : 72.7711 kJ / mol
• Heat atomization : 218 kJ / mol
• Heat of vaporization : 0.904 kJ / mol H2
• Number of skins : 1
• The oxidation state of minimum: -1
• electronegativity : 2.18 (scale Pauli)
• Configure electrons : 1s1
• The maximum oxidation state: 1
• Volume of polarization : 0.7 A3
• Structure : HCP (hexagonal close-packed) (solid H2)
• Atomic radius : 25 pm
• Thermal Conductivity : 0.1805 W / mK
• The atomic weight : 1.0079
• Ionization Potential : 13.5984 eV
Hydrogen gas is flammable. Hydrogen gas is explosive when mixed with air to form a volume ratio of 4% -75% and the chlorine with the volume ratio of 5% -95%. Hydrogen gas is very light due to the fire that caused the combustion of hydrogen gas tends to move upwards quickly so that Causes very little damage when compared with the fire that comes from burning hydrocarbons. This spontaneous reaction is usually in the trigger by a flash of fire, heat, or sunlight. Enthalpy of combustion of hydrogen gas is -256 kJ / mole by the reaction:
2 H2 (g) + O (g) -> 2H2O (l) + 572 kJ
Hydrogen is very reactive and reacts with every element of which is an oxidant and is more electronegative than hydrogen halide such as class. Hydrogen can react spontaneously with chlorine and fluorine at room temperature to form hydrogen halide.Hydrogen can also form compounds with elements that are less electronegative metal such as by forming a hydride. Hydrogen solubility in organic solvents is very small when compared with the solubility in water.
Hydrogen can be absorbed in a metal such as steel. The absorption of hydrogen by steel is causing the steel to be easily broken, so causing damage in the manufacture of equipment. With these properties, the scientists can store hydrogen in metal platinum ga.
At normal temperature of hydrogen contained in the form diatomiknya but at a very high temperature hydrogen dissociates into atomic-ataomnya. Atomic hydrogen is very reactive and can react with metal oxides such as silver, copper, timbale, bismuth, and mercury to produce free metal.
Atomic hydrogen can also react with organic compounds to form complexes such as with C2H4 to form C2H6 and C4H10.
At very high pressures of hydrogen can have properties such as metal
Ø CHARASTHERISTIC OF NITROGEN
A. Trends Nitrogen Group
The group element is 7N, 15P, 33As, 51Sb, 83Bi; two more first non-metallic elements, while the other three elements are metallic. This division is actually less accurate because of the difficulty of distinguishing between the two trait. Two characteristics that can be studied is the electrical resistance of the element in question and the nature of the acid-base oxidation as indicated by the table below.
Nitrogen and phosphorus both are not electrically conductive and form acid oxides so that no doubt both are classified as non-metallic. Classification problems began to appear on arsenic. General appearance allotropes of arsenic such as metal, but the sublimation and the recommendations produced in the form allotropes into two yellow powders. Because arsenic has two allotropes appearance such as metals and non-metals, and forming oxides amfoterik, the arsenic can be classified as semilogam. But many chemical compounds arsenic parallel with phosphorus, which can also be classified as non-metals. Antimony and bismuth are grouped near the boundary area as arsenic.
B. Nitrogen
Nitrogen or limp substance is a chemical element in the periodic table that has the symbol N and atomic number 7. Usually found as a gas without color, without odor, no taste and is a diatomic gas is not a stable metal, very difficult to react with other elements or compounds. Substance called weak because these substances are lazy, do not actively react with other elements.
Nitrogen in the air there is approximately 78.09% percent of the earth's atmosphere and present in many living tissues. Substance limp forms many important compounds such as amino acids, ammonia, nitric acid, and cyanide. Nitrogen is a non-metallic substances, with electronegativity 3.0. Has 5 electrons in its outer shell. Therefore trivalent in most compounds. Nitrogen condenses at a temperature of 77K (-196oC) at atmospheric pressure and freeze at a temperature of 63k (-210oC).
1.Aspek chemical nitrogen atom
Nitrogen atom with electronic configuration 1s2 2s2 2p3 can achieve a full valence electron configuration by four processes are:
a.Penangkapan 3 electrons to form the nitride anion, N3-, ions are only present in nitride compounds from salt-like metals are highly electropositive (such as lye).
b.Pembentukan electron pair bond as a single bond as in NH3, and three double bonds as in N2, or double as in the group-N = N-
c.Pembentukan electron pair bond with electron capture as the NH2-, HNH] - and NH2-, HN] 2 - d.Pembentukan electron pair bond with the release of electrons as in NH4 + and substituted ammonium ions [NR4] +
However, there are several stable nitrogen compounds with valence electron configuration is not full as in NO, NO2, and nitrous oxide in these compounds have unpaired electrons.
2.Sifat nitrogen anomaly
Single a.Ikatan
Nitrogen with three single bonds contained in NR3 compounds (R = H, alkali), which has a triangular pyramid shape. The occurrence of bond can be explained through sp3 hybrid orbitals with non-bonding electron pair or lone electron pairs occupy the position of one of the four corners of the tetrahedron structure, thus the actual molecular shape becomes visible as a triangular pyramid. Chemical aspects that are important in this compound related premises role of non-bonding electron pairs. With the non-bonding electron pair, all NR3 compounds act as Lewis base. Therefore, NR3 to form complex compounds with Lewis acid and can also act as ligands of transition metal ions.
Energy N-N single bond is relatively very weak. When compared to the CC single bond energy, there are very striking differences. This comparison to the elements preformance period 2 is 350, 160, 140, and 150 kJ mol-1, which respectively refer to a single bond energies in compounds H3C-CH3, H2N-NH2, HO-OH, and FF. This difference is probably something to do with the influence of repulsion between non-bonding electron pairs, that is not there, there are a pair, two pairs and three pairs for each compound. The low energy of this single bond, unlike carbon, resulted in little tendency for the formation of chains of nitrogen atoms.
b.Ikatan double / double
Nitrogen N2 form a stable molecule with three double bonds are very strong bond premises very short distance of 1.09 A. Very large binding energy, 942 kJ mol-1, much larger than the energy of three double bonds to phosphorus (481 kJ mol-1) and also greater than the energy three-carbon double bond (835 kJ mol-1). This can be explained that the nitrogen atom using one of the p orbitals for bonding ∞ and two others for the π bond. Phosphorus P4 molecules form a particular layer or structure with single bonds. If the nitrogen form a single bond and one double bond, then the non-linear molecular structure.
c.Absennya role of d orbitals
With fluorine, nitrogen only establish trifluoride, NF3, while phosphorus trifluoride formed pentafluorida PF3 and PF5. hybridization theory suggests that the phosphorus atoms in the hybridization sp3d PF5 experiencing, so involves the 3d orbitals in forming bonds PF; not possibly provide the nitrogen atom d orbitals, and therefore are not able to form analogous compounds.
d.Elektronegatifitas
Electronegativity of nitrogen is much higher than with other members in its class. As a result, the nature of the polarity of the bonding in nitrogen compounds are often contrary to the nature of the polarity of the bonding in compounds other members. NH covalent bond is very polar, then the ammonia is alkaline, while the other members of the hydride compound, fosfina PH3, AsH3 arsina, and stibina SbH3, is neutral.
3.Beberapa nitrogen compounds
a) Ammonia, NH3
Ammonia is a chemical with chemical formula NH3. Ammonia molecule has a triangular shape. Contained in atmospheric ammonia in a small quantity of organic matter due pereputan. Ammonia is also found in the soil, and in places close to the volcano. At temperatures and pressures expert, ammonia is a gas that has no color and is lighter than air (air ketumpatan 0589). Dissolution point is -75 ° C and its boiling point is -33.7 ° C. 10% solution of ammonia in water has a pH of 12. Ammonia in liquid form has a very high load haba.
In the ammonia molecule N central atom surrounded by three PEI and a pair of PEB, the ammonia molecule is pyramidal form a triangle; N atom is located at the top of the pyramid while the third H atom at the base of the pyramid.
b) Hydrazine, NH2-NH2
Hydrazine in aqueous solution made from the reaction of ammonia with hypochlorite, and is thought to occur by two reaction steps:
OCL-NH2Cl NH3 + + OH-
NH2Cl + OH-+ NH3 N2H4 + Cl-+ H2O
Overall reaction:
2 NH3 + OCl-N2H4 + Cl-+ H2O
In acidic or alkaline atmosphere, hydrazine is a strong reducing agent, widely used as a reducing component of rocket fuel preformance in the form of dimethyl hydrazine, (CH3) 2NNH2. Oxidation of hydrazine produces berbgai kinds of compounds depends on the type oksidatornya. Hydrazine structure similar to the structure of ethane, except in the case of one H atom from each cluster is replaced with a pair of electrons metilnya outs, this structure has a single NN bond length, 145 pm.
c) Nitride
Nitride is a metal compound N. In general, if the metal amide is heated will terjasdi deamoniasi into metal nitride such as in the following reaction:
3 Mg (NH2) 2 + 4 NH3 Mg3N2
A better method for pembutan nitride is heating a mixture of metals or metal oxides and carbon with nitrogen or ammonia
c) Nitrogen Halides, NX3
Famous florida nitrogen compounds are gaseous NF3 odorless, colorless and non-reactive, which can be made from electrolysis of molten ammonium biflorida or larutanya in anhydrous hydrogen fluoride. This compound is similar to ammonia, has one electron pasanga outs but are weak Lewis base
d) Acid hidrozoik or hydrogen azide, HN3
These acids in aqueous solution can be obtained from the oxidation of hydrazine with nitric acid according to the equation:
N2H4 HN3 + 2 HNO2 + H2O
Hidrozoik acid in the form of a colorless liquid boiling at 37 0C and frozen at -80 0C, gave off an odor of painful and highly toxic. Azide ion materials used for rescue in the form of gas bags in the car. To avoid touching the rider with sodium metal mixed with Fe2O3.
e) Nitrogen oxides and oxy acids
Nitrogen can be fused with oxygen to form oxides with varying degrees of oxidation, from +1 to +5, for example, N2O, NO, N2O3, N2O4, NO2 and N2O5. While the oxy acids of nitrogen that can be encountered is H2N2O2 (as.hiponitrit), HNO2 (as.nitrit), HNO3 (as.nitrat) and HNO4 (as.peroksinitrit).
Dinitrogen monoxide, N2O. Monovalent nitrogen oxides. Pyrolysis of ammonium nitrate will produce this oxide by the reaction:
NH4NO3 → N2O + 2 H2O (heating at 250 ° C).
Although oxidation is only a formality, it is interesting and symbolic how changes in the nitrogen oxidation to form monovalent NH4NO3 nitrogen oxides (+1 is the average of -3 and +5 oxidation state of N in NH4 + and NO3-). NNO bond distance in N2O is 112 pm (NN) and 118 pm (NO), respectively related to the bond order 2.5 and 1.5. N2O (16e) isoelectronic with CO2 (16 e). This compound is widely used for analgesia. Nitrogen oxide, NO. Divalent oxides of nitrogen. Obtained by reduction of nitrite via the following reaction:
KNO2 + KI + H2SO4 → NO + K2SO4 + H2O + ½ I2
Because an odd number of valence electrons (11 e), NO is paramagnetic. NO distance is 115 pm and has a double bond character. Unpaired electron in an orbital π * antiikatan easily removed, and NO to NO + (nitrosonium) is isoelectronic with CO. Because electrons are removed from the orbital antiikatan, NO bond becomes stronger. C
ompounds containing NOHSO4 NOBF4 and these cations are used as an oxidant and an electron.
Although monomeric NO as a paramagnetic gas, dimerization in the solid phase will produce diamagnetisme. NO is a ligand of transition metal complexes are unique and form complexes such as [Fe (CO2) (NO) 2], with NO is a neutral ligand with 3 electrons. Although the MNO bond on the straight in this type of complex, MNO bond angle turn to 120 ° - 140 ° in [Co (NH3) 5 (NO)] Br2, with NO-is ligand 4 electrons. Lately it became clear that NO has a variety of biological control functions, such as blood pressure reduction actions, and is the most important species, after Ca2 + ions, in signal transduction.
Dinitrogen trioxide, N2O3. Nitrogen oxidation number is +3 in this compound, the compound is unstable and will decompose into NO and NO2 at room temperature. This compound is produced when the equivalent quantity of NO and NO2 are condensed at low temperatures. The solid light blue, dark blue and will be colored when in liquid, but the colors will fade at higher temperatures.
Nitrogen dioxide, NO2, a nitrogen compound oxidation by nitrogen berbilangan +4. NO2 is a compound with an odd number of electrons with unpaired electrons, and reddish brown. These compounds are in equilibrium with dinitrogen tetraoksida dimer, N2O4, which is not colored. The proportion of NO2 is 0.01% at -11 ° C and increased slowly to 15.9% at the boiling point (21.2 ° C), to 100% at 140 ° C. N2O4 can be produced by pyrolysis of lead nitrate
2 Pb (NO3) 2 → 4NO2 + 2PbO + O2 at 400 oC
When NO2 is dissolved in nitric acid and water produced nitrite:
2 NO2 + H2O → HNO3 + HNO2
With one electron oxidation, NO2 + (nitroil) is formed and the bond angle changes from 134o to 180o in neutral NO2. On the other hand, the reduction of single electrons, ions formed NO2-(nitrito) with bond angle 115o.
Dinitrogen pentoxide, N2O5, is obtained when the concentrated nitric acid slowly dehydrated with phosphorus pentoxide at low temperatures. This compound sublimes at a temperature of 32.4o C. Karenadengan dissolving it in water will produce nitric acid, dinitrogen pentoxide is also called anhydrous nitric acid.
N2O5 + H2O → 2 HNO3
Although in the solid state dinitrogen pentoxide is an ion pair alternately NO2NO3 with ion sites are occupied by ions straight planar ion NO2 + and NO3-, in the state of this molecule is a molecular gas.
Ø CHARASTHERISTIC OF OXIGEN
A. Trends Oxygen Group
Oxygen, sulfur or sulfur and selenium, including non-metals, telirium semilogam and polonium as a metal in this class. The melting point and point dididh shows a typical trend for increased non-metals, followed by a tendency to decrease the typical start of polonium metal. This classification is supported by the data at very low electrical resistance for the metal polonium, jumped high for semilogam tellurium and selenium are very high for non-metallic. Except for oxygen, there are certain patterns concerning oxidation tingakat group elements 16, ie oxidation even. In general, the stability of -2 and +6 oxidation rate decreases with increasing atomic number, but the stability of the +4 oxidation rate increased, although this trend is not regular.
B. Anomalies Oxygen
1.Stabilitas double bond and the nature katenasi
Double bond on the oxygen is much greater than the single bond, single bond OO very weak relation to the establishment katenasi. In a class of carbon (class 14), the ability katenasi decreased with increasing atomic number, but the class of 16, the sulfur can form a chain that tepanjang (S8). In fact, a single bond to be weaker than the OO single bond oxygen atoms with other atoms, OX. Thus, oxygen atoms prefer to form bonds with atoms other than with himself.
2.Absennya d orbitals
Oxygen to form only one compound of fluorine that is OF2 premises, but the sulfur is able to form some compounds with fluorine including SF6. To achieve these six covalent bonds involving sulfur atoms have orbital d. Thus, not seen for oxygen-fluorine compounds that are analogous to SF6 related to the unavailability of d orbitals of oxygen atoms.
B. Oxygen
Allotrope of elemental oxygen which is generally found on earth is dioxygen O2. He has a length of belt 121 pm and the binding energy 498 kJ • mol-1. Allotrope of oxygen used by living things in the cell respiration and is a major component of the earth's atmosphere. Trioksigen (O3), known as ozone, an allotrope of oxygen is highly reactive and can damage lung tissue. Ozone is produced in Earth's atmosphere when O2 joined the atomic oxygen resulting from the separation of O2 by ultraviolet radiation (UV). Because ozone absorbs UV waves are very strong, the ozone layer in the atmosphere serves as a radiation shield that protects the planet. However, near the earth's surface, ozone is an air pollutant formed from automobile combustion byproducts.
Tetraoksigen metastable molecules (O4) was discovered in 2001, and assumed that there are at one of six phases of solid oxygen. It was proven in 2006, by pressing the O2 up to 20 GPa, and found the structure of rhombohedral Cluster O8. Cluster is potentially a more powerful oxidant than O2 and O3, and can be used in rocket fuel. Metal phase oxygen was found in 1990 when solid oxygen is pressed up above 96 GPa. Also found in 1998 that at very low temperatures, this phase becomes superconducting.
1.Ikatan oxygen in covalent compounds
Oxygen atom normally forms two single covalent bond-O-, or one double bond O =. If the oxygen atoms forming two single covalent bonds, the bond angle can vary less than the regular tetrahedral angle (109o 28 '), it is influenced by the number of electrons as predicted by theory menyendyri VESPR. Another way is the formation of the oxygen atom binds three single covalent bonds are equivalent. Oxygen can also form coordinate covalent bonds, both as sam Lewis who very rarely encountered, as well as Lewis base most commonly encountered.
2.Kecenderungan in oxygen compounds
• electropositive metal oxides are ionic strength and alkaline.
• Some basic oxide, such as copper (II) oxide is not soluble in water, but soluble in dilute acid.
• metal oxides such weak electropositive aluminum, zinc, and tin are amfoterik, which react with acids or bases.
• If a metal can form more than one kind of oxide, usually with metal oxides with low oxidation bertngkat is alkaline, and multilevel metal oxides with high oxidation are acidic.
• non-metallic oxides are always covalently bonded, for non-metallic brtingkat low oxidation tended to be neutral and to non-metallic high-rise tends to be acid oxidation.
3.Hidrogen peroxide
3.Hidrogen peroxide
Brupa pure hydrogen peroxide mixture is almost colorless, highly viscous because of the strong hydrogen bonding, and is corrosive. The structure forms an angle of 111o and the dihedral angle of 94.5 o bond HOO. Hydrogen peroxide is not stable in a thermodynamic, easy terdisproporsionasi.
Ø CHARASTHERISTIC OF PHOSFORUS
C. Phosphorus and Arsenic
1) Allotropes Phosphorus
Phosphorus is produced by the reduction of calcium phosphate, Ca3 (PO4) 2, with quartz rock and coal. Allotropes of phosphorus include white phosphorus, red phosphorus, and phosphorus in black. White phosphorus is a molecule with a composition of P4 (Figure 4.7). White phosphorus has a low melting point (mp 44.1o C) and soluble in benzene or carbon disulfide. Because phosphorus is pyrophoric and highly toxic white, white phosphorus must be handled with caution.
Structure of amorphous red phosphorus and its structure is not clear. Its main components are assumed to form chains of molecules formed by polymerization of P4 as a result of opening a PP bond. Red phosphorus is not pyrophoric and non-toxic, and is used in large amounts to produce a match, etc.. Black phosphorus is the most stable isotopes and obtained from white phosphorus at high pressure (about 8 GPa). Black phosphorus has a metallic luster and lamellar structure. Although the nature of semiconductor black phosphorus at normal pressure, black phosphorus showed metallic properties at high pressure (10 GPa).
Phosphorus compounds as ligands Tertiary phosphine, PR3, and tertiary phosphite, P (OR) 3, is a very important ligands in transition metal complex chemistry. In particular triphenylphosphine, P (C6H5) 3, trietil phosphine, P (C2H5) 3, and their derivatives are very useful ligands in many complexes, because it is possible to precisely control the electronic and steric properties by modifying substituennya (refer to section 6.3 (c) .) Although these ligands are sigma donors, these ligands can demonstrate character by changing substituennya pi receiver into accepting electrons Ph (phenyl), OR, Cl, F, etc..
Electron-accepting character sequence is estimated from CO stretch frequency and 13C NMR chemical shifts of metal carbonyl compounds substituted phosphine or phosphite is as follows (Ar is aryl and R is alkyl).
PF3> PCl3> P (OAR) 3> P (OR) 3> PAr3> PRAr2> PR2Ar> PR
On the other hand, C. A. Tolman has proposed at the end of the cone angle around the phosphorus ligand substituents on the distance of van der Waals contacts can be used as a parameter to measure the steric keruahan phosphine or phosphite. This parameter, called the cone angle, and has been used extensively. When a large cone angle, coordination number will decrease because of steric hindrance, and equilibrium dissociation constants and dissociation rate of phosphorus ligands become larger. Numerical expression steric effects are very useful and many studies have been done to study this.
2) Phosphorus Hydride, fosfina
Analog compound ammonia is fosfina, PH3, a colorless gas and is very toxic to the melting point - 133.5 0C and the boiling point of -88 0C. The nature of the polarity of the PH bond in Fosfina much lower than the NH bond in ammonia, so fosfina is a lewis base is very weak and do not form hydrogen bonds.
3) Phosphorus Oxide
Different from the nitrogen, phosphorus form that is only two mcam oxide P4O6 and P4O10. Both the form of a white solid at room temperature. The structure of both oxides is based on the structure of a triangular pyramid (tetrahedron) of white phosphorus, P4. Tetrafosfor heksaoksida tebentuk by heating white phosphorus in oxygen-limited environment, in turn heating in oxygen environment resulted tetrafosfor dekaoksida. Tetrafosfor dekaoksida often digunaka as drying agent for reacting violently with water to produce phosphoric san.
4) Phosphorus Chloride
4) Phosphorus Chloride
There are two kinds of phosphorus chloride is PCl3 a colorless liquid and a solid PCl5 are white. PCl3 has a triangular pyramid shape and adopt PCl5 bipiramida triangular shape in the vapor phase utetapi adopt PCl4 + PCL6-structure in the solid phase, a fact which indicates that the species is in the boundary region of stability of covalent-ionic nature.
5) Acid Phosphorus oxy
Three important phosphorus oxy acid is an acid (ortho) phosphoric acid, H3PO4, phosphorous acid or fosfonik acid, H3PO3, and acid or acid fosfinik hidrofosfat, H3PO2. In oxy acid, hydrogen atoms as the carriers of the acidic nature is always bound to oxygen atoms, and for the central atom polivalen difference formula contained in the loss of oxygen atoms bind hydrogen atoms are acidic nature of the carrier.
Arsenic
Arsenic, arsenic, or arsenic is a chemical element in the periodic table that has the symbol As and atomic number 33. It is a well-known toxic metalloids material and has three forms alotropik; yellow, black, and gray. Arsenic is usually located in a metallic form which has a structure similar to black phosphorus. Modifications such arsenic is very good for conductors but poor thermal conductors for electricity. Arsenic is chemically similar characteristics with Phosphorus, and often can be used as a substitute in a variety of biochemical reactions and are also toxic. When heated, arsenic will be quickly oxidized to arsenic oxides, which smell like the smell of garlic. Arsenic and some arsenic compounds can also be directly tersublimasi, changes from solid to gas without becoming liquid first. Basic substance of arsenic found in two forms of solid and metallic yellow, with a specific gravity of 1.97 and 5.73. Some places on earth contain arsenic high enough so that it can seep into groundwater. WHO set a safe threshold of the highest arsenic in ground water of 50 ppb (parts per billion). Most areas with the highest arsenic content is an area which is alluvial river silt and soil with rich organic matter. It is estimated that about 57 million people drink arsenic-contaminated ground water excess, thereby potentially poisoned. Arsenic in ground water is natural, and is released from sediments into ground water in the absence of oxygen in the layer below the soil surface. This ground water began to be used after western NGOs from the program examines the massive water wells at the end of the 20th century, but failed to find the presence of arsenic in groundwater. It is estimated as the worst mass poisoning in history and probably the worst environmental disasters in history. In Bangladesh there an epidemic of mass poisoning caused by arsenic.
Many other countries in Asia, like Vietnam, Cambodia, Indonesia, and Tibet, which allegedly has a similar geological environment and is conducive to producing ground water containing arsenic in high concentration.
Benefits of arsenic:
• Various kinds of insecticides and poisons.
• gallium arsenide is an important semiconductor material in integrated circuits. Circuits made using these components are much faster but also more expensive than made of silicon.
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