* Classification of the chemical elements
* For their reactivity
* For its usefulness
* For its economic impact
* For its environmental impact
* Toxic chemical waste
* Forest land became grassland and city
Classification of chemical elements: On the reactivity of its utility, for its economic impact, and environmental impact.
Classification of the chemical elements
In accordance with the Periodic Table of the chemical elements are classified as follows according to their physical properties:
Lactnidos and Actinides
Are chemicals which generally contain between one and three electrons in the final orbit, which can easily give way, which makes conductors of heat and electricity.
The metals, in general, are malleable and ductile, with a characteristic luster, varying intensity which depends on the motion of the electrons that make up the molecules.
Gold and silver, for example, have very bright and because of their physical characteristics are great conductors of electricity, but its high price in the market is preferred to employ as substitutes, copper and aluminum, cheaper metals and also good conductors.
75% of the chemical elements found in nature are metals and other noble gases nonmetals, and metalloids internal transition.
Metalloids: These are elements that have generally last four electrons in its orbit, so have properties intermediate between metals and nonmetals. These elements conduct electricity in only one direction, not allowing it in the opposite direction as in metals. The silicon (Si), for example, widely used is a metalloid in the manufacture of semiconductor elements for the electronics industry, as rectifier diodes, transistors, integrated circuits, microprocessors, etc..
No metals possess generally five to seven electrons in its final orbit. Because of that property, rather than its tendency is giving electrons to complete eight win in its last orbit. Nonmetals are poor conductors of heat and electricity, have no luster, are malleable and ductile not and, in solid form, are fragile.
Noble gases: chemical elements are inert, ie not react with other elements, for in his last orbit containing the maximum possible for that electron energy level (eight in total). The argon (Ar), for example, is a widely used noble gas inside incandescent and fluorescent lamps. Neon is also another noble or inert gas, widely used in lighting ornaments texts and ads and billboards and is extremely oxidizing chlorides with most elements.
For their reactivity
In the following summaries of the revived talk of some elements when mixed with another or just their large impact.
When combined with hydrogen to give hydrogen chloride in presence of diffused light reaction occurs slowly but when combined direct sunlight and an explosion shows a large amount of heat.
Chlorine is also combined with hydrogenated compounds such as hydrogen sulfide and ammonia forming hydrochloric acid with hydrogen thereof.
Many hydrocarbon decomposes but when controlling the reaction conditions is achieved by partial substitution of hydrogen chloride.
When red reversibly reacts with water vapor to form hydrochloric acid and releasing oxygen:
Cl2 + H2 O = 2HCl + 1/2 O2
In cold and in the presence of light, reacts slowly with hydrochloric acid and water to give hypochlorous acid HClO, which in turn decomposes to form oxygen. This is why the oxidizing power of the chlorine water.
May form chlorides with most metals albeit in different conditions and with different intensity. For example, cold sodium reacts slowly, but if heated too bright flame burns with sodium chloride formed.br> also reacts with iron and copper, but if it is completely dry and no reaction occurs. Therefore cylinders may be stored in iron or steel.
The chlorine water can dissolve the gold and platinum metals that are very resistant to chemical agents.
If dissolved in substances that provide a large concentration of hydroxyl ions forming a mixture of chloride and hypochlorite. For example sodium hydroxide (caustic) chloride gives a mixture of sodium hypochlorite call Javel water.
Chlorine combines directly with most non-metallic elements, except the carbon, nitrogen and oxygen (which if known chlorides, although indirectly obtained). For example with phosphorus trichloride to form combined phosphorus, and phosphorus pentachloride if excess chlorine.
Summary of Reactivity
Chlorine is a greenish yellow gas with pungent odor and irritating, poisonous dense and can be liquefied easily to the pressure of 6.8 atmospheres and 20 C.
The gaseous chlorine is dissolved in water quite good: at atmospheric pressure and at 0 C, 1 liter of water dissolves approximately 5 liters of gaseous chlorine to give a solution which is known as chlorine water which can crystallize a hydrate. Calcium reacts violently with water to form the hydroxide Ca (OH) 2 off hydrogen. Aluminium reacts easily with HCl, NaOH, perchloric, but generally resists corrosion due to rust. However when Cu + + and Cl-its passivation disappears and is very reactive.
The alkyls, used in the polymerization of ethylene,  are so reactive that destroy human tissue and exothermic reactions occurring on exposure to air and water.  Magnesium also reacts with hydrochloric acid (HCl) to produce heat and hydrogen is released into the environment in form of bubbles. At high temperatures the reaction occurs even faster.
Magnesium is a highly flammable metal, which easily combusted when in the form of chips or powder, while in bulk form is less flammable solid. Once ignition is difficult to extinguish because it reacts well with nitrogen present in the air (forming magnesium nitrate) and carbon dioxide (forming magnesium oxide and carbon).
For its utility
Then explain some elements which are most used
Calcium ions act as a cofactor in many enzyme reactions, involved in glycogen metabolism, together with the potassium and sodium regulate muscle contraction. The percentage of calcium in organisms is variable and depends on the species, but on average accounts for 2.45% of all living beings, in plants, represents only 0.007%.
In common speech the word is used to refer to calcium aluminum salts This metal has a combination of properties that make it useful in mechanical engineering, such as low density (2,700 kg/m3) and high corrosion resistance. By suitable alloys can significantly increase its mechanical resistance (up to 690 MPa). It is a good conductor of electricity, it machines easily and is relatively inexpensive. Therefore, it is the most widely used metal after steel. Under normal conditions of pressure and temperature, the oxygen is in a gaseous form diatomic molecules (O2) to be unstable although produced during photosynthesis by plants and are subsequently used by animals in breathing (see cycle oxygen). Can also be found in liquid form in laboratories. If reaches a temperature below -219 C, is converted into a blue crystalline solid. Its valence is 2.
Copper is part of a very high amount of alloys generally have better mechanical properties, though they have a lower electrical conductivity. The most important are known by the name of bronzes and brasses. Moreover, copper is a durable metal that can be recycled an almost unlimited number of times without losing their mechanical properties.
He was one of the first metals to be used by humans in prehistory. Copper and its alloy with tin, bronze, acquired such importance that historians have called the Copper Age and the Bronze Age to two periods of antiquity. Although its use lost relative importance to the development of steel, copper and its alloys remained employed for such diverse objects as coins, bells and cannons. From the nineteenth century, specifically the invention of the electric generator in 1831 by Faraday, copper again became a strategic metal, being the main raw material of cables and wiring.
Copper has an important biological role in the process of photosynthesis of plants, although not part of the composition of chlorophyll. The copper contributes to the formation of red blood cells and maintenance of blood vessels, nerves, bones and immune system and therefore is a trace element essential for human life. 
Copper is found in a lot of habitual dietary foods such as oysters, seafood, vegetables, organ meats and nuts among others, in addition to water and therefore it is very rare that there is a deficiency of copper in the body. The copper imbalance in the body causes a liver disease known as Wilson’s disease. 
Copper is the third most widely used metal in the world, behind steel and aluminum. The world refined copper production was estimated at 15.8 Mt in 2006, with a deficit of 10.7% compared to the projected global demand of 17.7 Mt  The fuels are bodies capable of combining with oxygen with evolution of heat. The products of combustion are usually gaseous. For practical reasons, the combustion must be neither too fast nor too slow.
It can be distinguished from the fuels burned in homes and fuels used in internal combustion engines, although all fuels can be used as fuel, not true the vice versa.
Classification and use of fuels:
The different fuels and fuels used can be: solid, liquid or gaseous.
Metals: production and applications
For its economic impact
The following paragraphs explain some of the great economic impact elements.
Fuels and fuel. The fuels are bodies capable of combining with oxygen to release heat. The products of combustion are usually gaseous. For practical reasons, the combustion must be neither too fast nor too slow. It can be distinguished from the fuels burned in homes and fuels used in internal combustion engines, although all fuels can be used as fuel, not true the vice versa. Classification and use of fuels: The different fuels and fuel used can be: solid, liquid or gaseous. Solid fuels.
Natural Coals: natural coals come from the slow transformation, out of contact with air, plant masses accumulated in certain regions during geological times. The carbonization process, in some cases, very old, as well as influencing other factors such as environmental conditions and the nature of the original plant. They have issued numerous theories to explain the formation of the coal mines, but none is entirely satisfactory. Wood: The wood is mostly used in home heating. In industrial households, except in countries where it is very abundant, is rarely used.
Liquid fuels. Oil: Found in certain regions of the world (United States, Venezuela, USSR, etc.) In underground deposits, is extracted by drilling holes that can reach 7000 m depth. crude oil, and water containing sand, is brought to a settling container; if not refined at the extraction site, it is transported by means of drawn steel pipe of an inner diameter of 5 to 35 cm, which are called pipelines or pipelines. The crude, liquid highly variable aspect is an extremely complex mixture of many hydrocarbons, with minor amounts of other substances. Depending on their origin, predominantly saturated hydrocarbons or cyclic hydrocarbons, but all crude oil both types exist in variable proportions.
Gaseous fuels. Natural Gas: In the interior of the earth’s crust are bags containing large amounts of combustible gases whose origin is probably analogous to the oils. The pressure of these gases is generally high, enabling economic distribution to large regions. They consist mainly of methane, with small amounts of butane, and even by liquid hydrocarbons. These, when recovered, are a good source of fuel. Propane and butane are collected from crude oil in which they are dissolved. Also originate from the various treatment operations oils. They are easily liquefied at low pressure and can be transported as a liquid in light metal containers. They are used as domestic gas in regions where there is no gas for lighting distribution.
Hydrogen: The pure hydrogen, generally produced by the electrolysis of water is not used as fuel in welding and in the manufacture of synthetic gemstones. In this case it is irreplaceable: as not containing carbon, there is no danger of altering the transparency of the stones. Acetylene is obtained by action of water on calcium carbide. It gives a very hot flame and very bright. It is used in welding and lighting, but these are ancillary applications: acetylene is, above all, an important intermediate in many industrial chemical synthesis
For its environmental impact
In the following summary we find that elements are very harmful to the environment and humans:
Since the lead found in nature in the form of carbonate, sulfate and almost all trade lead sulfide is obtained which constitutes the galena ore.
It is a gray metal, heavy, little soft and resistant to traction. Freshly cut bright surface exposed to air, rapidly oxidizing fogs, the opaque layer of oxide protects it from further attack.
Lead reacts very slowly with hydrochloric acid, and sulfuric acid and cold just attacking him, by forming insoluble sulfate that preserves for their subsequent work. Lead in contact with hard water is coated with a protective layer of insoluble salts such as sulfate, bicarbonate or phosphate base. Distilled water from rain and containing no dissolved substances capable of forming this film, attack the metal to cause the dissolved oxygen carrying and form lead hydroxide, somewhat soluble.
Soluble lead compounds are poisonous, and therefore, lead pipes to conduct water can be used safely only if the water is somewhat hard.
Lead is used for manufacture of pipes and tubes coated wires. Also used are sulfuric acid plants and in lead accumulators.
Lead fumes are causing a big disease called poisoning, characterized among other symptoms of anorexia, persistent constipation, anemia, muscle paralysis, insomnia, anxiety etc. It usually affects miners who extract lead, painters and printers who manufacture batteries.
There are important differences in the epidemiology, clinical manifestations of lead poisoning in children and adults.
In children, the disease must be due to malacia or pica (appetite perversion that leads children to eat things unfit for nutrition) or nibble of objects decorated with lead paint.
In adults, lead poisoning is commonly professional home but rarely can be caused by consuming contaminated food or drinks.
Symptoms in children include abdominal pain, vomiting, drowsiness, irritability, weakness or convulsions coma, signs of elevated intracranial pressure.
In adults: anorexia, constipation, discomfort, bowel, weakness, fatigue, headache, pallor. In severe cases there may be abdominal cramps. The lead line can only appear when the deficiency is oral hygiene.
Arsenic is found free in nature, and combined in various minerals realgar red orpiment yellow mispiquel
O arsenical pyrite, and arseniosita cobaltite.
Arsenic trioxide is obtained by roasting arsenic minerals, it oxidizes sublimes and is collected as a white powder in the fireplace.
Arsenic is a brittle solid, crystalline, gray steel. Sublimes easily, forming toxic fumes yellow alaci odor.
Arsenic exists in three allotropic forms: gray crystalline, amorphous yellow and black crystal.
The yellow variety is analogous to white phosphorus. The variety structurally resembles gray violet phosphorus.
Arsenic is relatively inert at ordinary temperatures, but heated air burns like white clouds blue flame producing solid trioxide.
Although all soluble arsenic compounds are poisonous, some have medicinal use. Those who consume acquire some tolerance to it and can take larger amounts of other people who are not used.
Arsenic compounds are used in agriculture, livestock sprays and bathrooms, in order to destroy insects and parasites.
Symptoms of ingestion of arsenic are:
Metallic taste, burning pain in the esophagus and stomach cramps, vomiting and profuse diarrhea with feces “rice water”. Followed by bloody stools, depression, extreme thirst, dry mouth and throat, feeling of constriction in the throat, garlic odor of breath and feces, dizziness, headache central, muscle cramps, skin cold, viscous, Pulse small, rapid and weak , cold extremities, cyanosis, breathing hard, stupor, circulatory collapse, convulsions, coma, rashes, oliguria, albuminuria, hematuria.
It is found in nature in a weight ratio of just over 0,003% and usually occurs in combination, especially in the form of oxide or cassiterite, very abundant in Bolivia, Indonesia, and Malacia.
Pewter is a white metal, softer than zinc, but harder than lead. At 200 C it becomes very brittle and may be sprayed.
Tin is used as a protective coating of iron in the tin. The tin is used to make boats and the like.
Tin also used in the manufacture of alloys, such as man (copper, tin), weld metal (tin, lead), and type metal (tin, lead and antimony.
Tin rich alloys used to make the bearing metal (white metal), which is coated with the inner face of the bearing. The lead alloy is the basis of so-called soft solders.
The stannic oxide are discretely harmful if inhaled and heavy dose may result in increased temperatures, usually repeated inhalation cause neuropathy.
Stannic chloride can cause bronchial irritation and pulmonary enema.
Organotin derivatives are highly toxic, can cause agitation and delirium box that often follow a coma with intracranial hypertension.
It is native in nature in some cases, but is most abundant mineral cinnabar. Represents only 0.5 ppm of the Earth’s crust.
It is the only metal that, at ordinary temperatures, the liquid state adopts.
No rust in the air at ordinary temperatures but combines with oxygen slowly when kept in the atmosphere near its boiling point. For its general inactivity and reduced vapor pressure, vacuum pumps are used, and in the laboratory, to confine gases.
At elevated temperatures, the mercury vapor conducts electric current.
The mercury forms amalgams with many metals, when the proportion of liquid metal is another small but solid to pasty and to increase this proportion. Amalgam of tin, silver and gold used in dentistry.
Despite their beneficial medical applications, mercury poisoning causes some (like mercurial stomatitis and hidragirismo) affecting various organs, especially the kidneys and the digestive and nervous.
Acute mercury poisoning:
Symptoms: When the poison is ingested in concentrated produces: Jan burning pain of mouth, throat and stomach, salivation, pain, cramps, severe vomiting, nausea, diarrhea, copious loss of fluids.
Chronic mercury poisoning:
This poisoning can result from inhalation of mercury vapors or dust of mercurial salts. The mercury can be absorbed through intact skin.
Alkyl mercury compounds can cause delusions, excitement followed by depression, which may be severe and long lasting.
As is more volatile than zinc, cadmium content in zinc ores found in the first metal portion is obtained, is separated by fractional distillation of zinc. It is also separated and recovered in the electrolytic refining of zinc. If the voltage is regulated only deposited zinc suitably pure cadmium is in the anode mud which is recovered by distillation.
Cadmium is white with bluish light, being much more malleable than zinc.
It is mainly used in the preparation of alloys of low melting point to fire extinguishers and automatic fuses, and also for coating iron, in order to protect from oxidation. Cadmium rods used in nuclear reactors to regulate absorb neutrons and fission process.
Soluble salts are most important cadmium chloride, and sulfate efflorescent. The hydrated cadmium ion is a weak acid.
Ingestion: abdominal cramps and violent stomach, vomiting, diarrhea. Inhalation: dry throat, cough, chest constriction feeling; brown discoloration of urine (cadmium oxide): designed intense, cold skin.
It is a bright white metal with bluish gray luster, soluble in acids and alkalis and insoluble in water. Constitutes 0.013% of the Earth’s crust. Is not native, although often small proportion lies in the composition of different rocks.
The ore used in the zinc metallurgy are oxide, carbonate and sulphide.
The zinc metal is brittle at ordinary temperature, but malleable between 120 and 150 C while maintaining its flexibility after cooling.
The metal is chemically active and displaces hydrogen from dilute acids, although its action is very slow when pure. Not altered in dry air, but in the wet oxidized, being coated with an adherent film of basic carbonate protecting it from any further action. Sufficiently heated in the air as greenish flame burning, giving white zinc oxide.
Zinc is used for roofing, gutters and cornices.
It is also used as the anode electric batteries, and is part of alloys such as Babbitt metal brass and German silver.
Sulfur is a necessary element for life in small quantities. The sulfate salt is one of the most abundant of the sea. Sulfur is seldom a limiting factor for plants, except on very poor soils or swamps distant ocean. Plants use sulfur to organic substance that goes into the food chain, is released as waste and decomposed after it returns to water as sulfate. This part of the cycle, Figure 25.2 is similar to the phosphorus cycle in Figure 2.3 and the nitrogen cycle
Some of the organic matter of vegetable production, with sulfur, peat and enters in aquatic sediments, and eventually becomes coal and oil. When water is filtered in organic deposits, the sulphate content in the water is transformed into hydrogen sulphide by microorganisms which use oxygen sulphate. Some reactions with iron salts are sulphates of iron particles (yellow mineral called “fool’s gold”), so as coal and oil are enriched with sulfur.
When burning coal and oil, sulfates minerals combine with oxygen to form sulfur gases (SO2 and SO3). When these gases are mixed with rain, are sulfur acids, in other words, becomes acidic rain. Some of nitrogen acids contribute through a similar process.
When acid rain falls on mountain lakes, the acid dissolves aluminum, which then clogs the gills of fish. Acid rain also removes nutrients. Many trees killed by acid rain. Countries through which pass winds industrial areas of the world, are being harmed by acid rain.
If acid rain falls on limestone (calcium carbonate) or soils with particles of calcareous salts, the acid is neutralized. These areas are less affected than those without limestone.
The combination of smoke and fog is called smog. This is a serious problem especially in areas with atmospheric inversion (a layer of warm air over a layer of cold air over the surface), causing the smoke from industrial areas of the city is situated. The air inversion prevents the rise of the surface and mix with the hot air. Smog causes respiratory problems and damages the growth of plants and trees. London, Madrid, Los Angeles and Mexico are examples of highly polluted cities, where they have already presented serious problems caused by high levels of smog.
Accumulation of carbon dioxide and the greenhouse effect.
Modern industries, released carbon dioxide (CO2) so quickly that the world’s trees and other plants, unable to synthesize photo. In addition, the green areas are becoming smaller, humans are using these extensions as agricultural land and industrial facilities and residences.
The percentage of CO2 in the air grew more than 20% in the last century, this extra layer of CO2 in the atmosphere acts like the glass in a greenhouse. The effect of this increase in temperature has on the Earth’s atmosphere and climate, is the subject of many scientific studies and is controversial. It is unclear whether sea level is falling or rising.
One theory is that the temperature increase caused by the increase of CO2 in the atmosphere will increase the temperature around the Earth, causing melting poles and rising sea level.
Another theory is that this extra heat raises the temperature of the tropical seas, causing more water evaporation, more clouds, rain and snow away from the tropics. At the poles, falls as snow. Extra snow and ice reflect more light, making these areas become colder, more snow and ice forming. When there is more snow and ice during the winter than can melt during the summer, increasing the permanent snowfields and glaciers, as in Greenland and Antarctica. Retaining water in the form of ice, in the continental plate, sea level drops worldwide. With the poles colder and warmer tropical seas, the temperature contrast is great. Although the climate system is a heat engine that works with the contrast in temperature between the poles and the tropics, the temperature difference causes strong winds and storms.
The annual fuel use in the world today is growing slightly. In short, due to a shortage of fuel consumption in the world will start to decrease. With less fuel available, it is believed that more areas on Earth again be green and carbon dioxide in the air will begin to decline.
Ozone (O3) in the upper part of the atmosphere absorbs most of ultraviolet (UV) radiation from the sun. Excess ultraviolet light can cause damage, such as burns and skin cancer in humans. A controversy arises because of the destruction they are causing some chemicals, such as chlorofluorocarbons and Freon, the ozone layer.
Ozone is also formed in the smog, the sun acts on industrial chemicals placed in the atmosphere. High concentrations of ozone in the Earth’s surface cause lesions in the trees and respiratory problems in humans. Excessive concentration of industries in areas where winds are light and temperature inversion occurs, stop the normal process of air purification in the biosphere.
Water Eutrophication from excess nutrients.
The over-enrichment of water is caused by drainage from agricultural fertilizers, stormwater cities, detergents, mine waste and human waste drain. When these residues increase the concentration of nutrients (phosphates, nitrates, and potash primarily) of rivers and lakes, can cause excessive eutrophication. The nutrients stimulate the growth of algae and plants, which interfere with the use of water for drinking or recreation; these entries, usually irregular, causing waves of growth, followed by periods of excessive consumption that can use all the oxygen and kill the fish .
Toxic chemical waste
The main problem today, industries wherever there is the toxic chemical residue. The reservoir storage is only temporary, and infiltration begins to poison water supplies. Some components that nature can not detoxify never be used. Other than nature can handle, must be returned to the ecosystems that are able to detoxify it, in small concentrations and in special situations, away from people.
The solution is recycled for most contaminants. The waste water should be discharged in wetlands, but in volumes that are within the scope of nature. Trees and grasses of wetlands, nutrients can be used to increase growth and can absorb heavy metals in their biomass. Excess water, after being purified by plants, can seep through the soil into underground streams. Until acids in mining wastewater can be reused by wetlands, which are naturally acidic.
Solid waste includes household waste, scrap automobiles and machinery. The waste treatment in cities is very expensive. The usual method of health aterro has two serious drawbacks: it occupies valuable space, and toxic wastes normally infiltrate, poisoning groundwater. Recent studies suggest that recycling is not only cheaper, it can also be a positive contribution to the economy. The process involves first separating reusable glass and metals, after fragmenting the paper and plastic to be used as “straw” to protect the roots and small plants to reforest.
Translators note: Of course, one might add that the recycling process is a positive contribution to the economy, as long as the product contains no recycled waste to toxic chemicals, and then require a particularly expensive treatment, to remove them, and thereby prevent harmful contamination would occur by recycling these byproducts chemically contaminated in the middle.
Channeling and dredging
Dredging channels for navigation and control of water levels, has been redirected and disturbed many rivers and estuaries. While economic value increases by the development of water transport, most of the dredging causes, without the loss of other values important to the economy. For example: drain and build dams on wetlands eliminates the many services they provide us, such as water purification, receiving sediments that enrich the soil and rich vegetation.
In many areas, such as in the Netherlands and lands near the Nile and the Mississippi, the constant construction of dikes is needed to deal with the energy of nature. As fossil fuels become more difficult to obtain, and more expensive, some of that work will stop, and the lands and waters return to their natural state. Planning human facilities, so as to be in harmony with nature and use, it is best to spend scarce resources to combat a potential source of profit.
Forest land became grassland and city
People, as civilization advanced, were tearing down forest areas, farms or properties making them first and then cities. Despite being somewhat reforesting, deliberately and by natural processes, most of the world is still losing their forest areas. In Europe, cutting and reforestation are almost even, in a few areas, like the eastern United States and western Soviet Union, there is a net increase in forest areas.
Rotation of the soil.
The impact of modern agriculture on soil has been exhausting, end their nutrients and structure. Crop rotation can help, for example, when corn plantings, which consume soil nitrates, alternate with soy plantations, which return nitrates to the soil. After many years of use, the soil needs to ‘rest’ to rebuild its structure and content, allowing vegetation to grow back area. The soil is regenerated faster with growth of native trees and plants. Sometimes, when the seeds of native plants can not grow by natural means, can be introduced or replaced by exotic plants.