Chemical elements and its applications in everyday materials

INTEGRATIVE ACTIVITY

Chemical elements and its applications in everyday materials

EQUIPO: NATALIA DAENNA GONZÁLEZ VIERA VALERY SELENE GARCÍA MORALES ANETTE MONSERRAT SALAZAR ESQUIVEL EDUARDO ORTEGA CORPUS LUIS ROBERTO GONZÁLEZ GUAJARDO

Universidad Autónoma de Nuevo León Preparatoria No. 9 - Group 120 Stage 3 - Integrative Activity Date: 21/10/16

DEVELOPMENT

A chemical element, or an element, is a material which cannot be broken down or changed into another substance using chemical means. Elements may be thought of as the basic chemical building blocks of matter.

Depending on how much evidence you require to prove a new element has been created, there are 117 or 118 known elements.

A chemical element is the simplest form of matter that cannot be broken down using any chemical means. Any substance made up of one type of atom is an example of that element. All atoms of an element contain the same number of protons. For example, helium is an element -- all helium atoms have 2 protons. Other examples of elements include hydrogen, oxygen, iron, and uranium. • While every atom of an element has the same number of protons, the number of electrons and neutrons can vary. Changing the number of electrons forms ions, while changing the number of neutrons forms isotopes of an element. • The same elements occur everywhere in the universe. Matter on Mars or in the Andromeda Galaxy consists of the same elements found on Earth. • The elements were formed by nuclear reactions inside stars.

Initially, scientists thought only 92 elements occurred in nature, but now we know many of the short-lived radioactive elements are also made in stars.

Chemical elements constitute all of the ordinary matter of the universe.

However astronomical observations suggest that ordinary observable matter is only approximately 15% of the matter in the universe: the remainder is dark matter, the composition of which is unknown, but it is not composed of chemical elements. The two lightest elements, hydrogen and helium were mostly formed in the Big Bang and are the most common elements in the universe. The next three elements (lithium, beryllium and boron) were formed mostly by cosmic ray spallation, and are thus more rare than those that follow. Formation of elements with from six to twenty six protons occurred and continues to occur in main sequence stars via stellar nucleosynthesis. The high abundance of oxygen, silicon, and iron on Earth reflects their common production in such stars. Elements with greater than twenty-six protons are formed by supernova nucleosynthesis in supernovae, which, when they explode, blast these elements far into space as supernova remnants, where they may become incorporated into planets when they are formed.

The modern periodic table is similar to the periodic table developed by Mendeleev, but his table ordered elements by increasing atomic weight. The modern table lists the elements in order by increasing atomic number (not Mendeleev's fault, since he did not know about protons back then). Like Mendeleev's table, the modern table groups elements according to common properties. Element groups are the columns in the periodic table. They include alkali metals, alkaline earths, transition metals, basic metals, metalloids, halogens, and noble gases. The two rows of elements located below the main body of the periodic table are a special group of transition metals called the rare earth elements. The lanthanides are the elements in the top row of the rare earths. The actinides are elements in the bottom row.

Symbol: Li Atomic Number: 3 Atomic Weight: 6.939 Lithium is a member of the alkali group of metals. It is soft, silvery-white in color with the symbol Li, located under number 3 in the table. The other alkali metals are sodium, cesium, rubidium, potassium, and francium.

Alkali metals are similar in that as you go down the table, their electro-negativity is reduced while their reactivity increases. Their boiling and melting points also decrease when moving in this direction.

Source: Lithium does not occur as a free element in nature. It is found in small amounts in ores from igneous rocks and in salts from mineral springs. Pure lithium metal is produced by electrolysis from a mixture of fused (molten) lithium chloride and potassium chloride.

Isotopes: Lithium has 7 isotopes whose half-lives are known, with mass numbers 5 to 11. Naturally occurring lithium is a mixture of its two stable isotopes 6Li and 7Li with natural abundances of 7.6% and 92.4% respectively.

A soft, silvery metal. It has the lowest density of all metals. It reacts vigorously with water.

Lithium is soft and silvery white and it is the least dense of the metals. It is highly reactive and does not occur freely in nature.

Freshly cut surfaces oxidize rapidly in air to form a black oxide coating. It is the only common metal (but see radium) that reacts with nitrogen at room temperature, forming lithium nitride.

Lithium burns with a crimson flame, but when the metal burns sufficiently well, the flame becomes a brilliant white.

Lithium has a high specific heat capacity and it exists as a liquid over a wide temperature range.

The most important use of lithium is in rechargeable batteries for mobile phones, laptops, digital cameras and electric vehicles. Lithium is also used in some non-rechargeable batteries for things like heart pacemakers, toys and clocks.

Lithium metal is made into alloys with aluminium and magnesium, improving their strength and making them lighter. A magnesium-lithium alloy is used for armour plating. Aluminium-lithium alloys are used in aircraft, bicycle frames and high-speed trains.

Lithium oxide is used in special glasses and glass ceramics. Lithium chloride is one of the most hygroscopic materials known, and is used in air conditioning and industrial drying systems (as is lithium bromide). Lithium stearate is used as an all-purpose and high-temperature lubricant. Lithium carbonate is used in drugs to treat manic depression, although its action on the brain is still not fully understood. Lithium hydride is used as a means of storing hydrogen for use as a fuel.

Lithium is corrosive, causing skin burns as a result of the caustic hydroxide produced in contact with moisture. Women taking lithium carbonate for bi-polar disorder may be advised to vary their treatment during pregnancy as lithium may cause birth defects.

Symbol: C Atomic Number: 6 Atomic Weight: 12.01115 Carbon (atomic number 6, symbol C) is a chemical element, which is tetravalent and nonmetallic. It is among the few elements that have been known to people since antiquity. Carbon has several allotropes, among which are amorphous carbon, diamond, and graphite. Depending on the allotropic form, carbon's physical properties can vary widely. Graphite, for instance, is black and opaque, while diamond is very transparent. Graphite is so soft that it can produce a streak on paper while diamond is one of the hardest materials. Graphite has good conductor properties, and diamond has poor electrical conductivity.

Source: Carbon can be obtained by burning organic compounds with insufficient oxygen. The four main allotropes of carbon are graphite, diamond, amorphous carbon and fullerenes.

Natural diamonds are found in kimberlite from ancient volcanoes.

Graphite can also be found in natural deposits.

Fullerenes were discovered as byproducts of molecular beam experiments in the 1980s.

Amorphous carbon is the main constituent of charcoal, soot (carbon black), and activated carbon.

Isotopes: 13 whose half-lives are known, with mass numbers 8 to 20. Naturally occurring carbon is a mixture of two isotopes and they are found in the percentages shown: 12C (99%) and 13C (1%).

Isotope 14C, with a half-life of 5730 years, is widely used to date carbonaceous materials such as wood, archeological specimens, etc. for ages up to about 40 000 years.

There are a number of pure forms of this element including graphite, diamond, fullerenes and graphene.

Diamond is a colourless, transparent, crystalline solid and the hardest known material. Graphite is black and shiny but soft. The nano-forms, fullerenes and graphene, appear as black or dark brown, soot-like powders.

Carbon can exist with several different 3 dimensional structures in which its atoms are arranged differently (allotropes).

Three common crystalline allotropes are graphite, diamond, and (usually) fullerenes. Graphene has a 2D crystal structure.(Fullerenes can sometimes exist in amorphous form.)

Carbon is unique among the elements in its ability to form strongly bonded chains, sealed off by hydrogen atoms. These hydrocarbons, extracted naturally as fossil fuels (coal, oil and natural gas), are mostly used as fuels. A small but important fraction is used as a feedstock for the petrochemical industries producing polymers, fibres, paints, solvents and plastics etc.

Impure carbon in the form of charcoal (from wood) and coke (from coal) is used in metal smelting. It is particularly important in the iron and steel industries.

Graphite is used in pencils, to make brushes in electric motors and in furnace linings. Activated charcoal is used for purification and filtration. It is found in respirators and kitchen extractor hoods.

Carbon fibre is finding many uses as a very strong, yet lightweight, material. It is currently used in tennis rackets, skis, fishing rods, rockets and aeroplanes.

Industrial diamonds are used for cutting rocks and drilling. Diamond films are used to protect surfaces such as razor blades.

The more recent discovery of carbon nanotubes, other fullerenes and atom-thin sheets of graphene has revolutionised hardware developments in the electronics industry and in nanotechnology generally.

150 years ago the natural concentration of carbon dioxide in the Earth’s atmosphere was 280 ppm. In 2013, as a result of combusting fossil fuels with oxygen, there was 390 ppm. Atmospheric carbon dioxide allows visible light in but prevents some infrared escaping (the natural greenhouse effect).

This keeps the Earth warm enough to sustain life. However, an enhanced greenhouse effect is underway, due to a human-induced rise in atmospheric carbon dioxide. This is affecting living things as our climate changes.

Pure carbon has very low toxicity. Inhalation of large quantities of carbon black dust (soot/coal dust) can cause irritation and damage to the lungs.

Symbol: Si Atomic Number: 14 Atomic Weight: 28.086 Silicon (atomic number 14, symbol Si) is a metalloid and a chemical element which is solid at room temperature. It was isolated in 1824 by the Swedish chemist Jons Berzelius who also identified elements such as cerium, thorium, and selenium. Silicon is one of the most abundant elements in the universe, together with helium, hydrogen, carbon, nitrogen, neon, and oxygen. It is one of the most abundant elements in the earth's crust as well, along with calcium, iron, aluminum, and oxygen.

Source: Silicon is the second most abundant element in Earth’s crust, after oxygen and the eighth most abundant in the Universe. It is most commonly found as silicon dioxide (silica). Two elements, silicon and oxygen, make up almost three-quarters of our planet’s crust.

Commercial quantities of silicon are obtained by the reaction of silicon dioxide and carbon in an electric furnace using carbon electrodes. The carbon reduces the silicon dioxide to silicon. Silicon produced in this way is about 98% pure.

Isotopes: Silicon has 14 isotopes whose half-lives are known, with mass numbers 22 to 36.

Naturally occurring silicon is a mixture of its three stable isotopes and they are found in the percentages shown: 28Si (92.2%), 29Si (4.7%) and 30Si (3.1%).

The element, when ultrapure, is a solid with a blue-grey metallic sheen.

Silicon is a hard, relatively inert metalloid and in crystalline form is very brittle with a marked metallic luster.

Silicon occurs mainly in nature as the oxide and as silicates.

The solid form of silicon does not react with oxygen, water and most acids.

Silicon reacts with halogens or dilute alkalis.

Silicon also has the unusual property that (like water) it expands as it freezes.

Four other elements expand when they freeze; gallium, bismuth, antimony and germanium.

Silicon is one of the most useful elements to mankind. Most is used to make alloys including aluminium-silicon and ferro-silicon (iron-silicon). These are used to make dynamo and transformer plates, engine blocks, cylinder heads and machine tools and to deoxidise steel.

Silicon is also used to make silicones. These are silicon-oxygen polymers with methyl groups attached. Silicone oil is a lubricant and is added to some cosmetics and hair conditioners. Silicone rubber is used as a waterproof sealant in bathrooms and around windows, pipes and roofs.

The element silicon is used extensively as a semiconductor in solid-state devices in the computer and microelectronics industries. For this, hyperpure silicon is needed. The silicon is selectively doped with tiny amounts of boron, gallium, phosphorus or arsenic to control its electrical properties.

Granite and most other rocks are complex silicates, and these are used for civil engineering projects.

Sand (silicon dioxide or silica) and clay (aluminium silicate) are used to make concrete and cement.

Sand is also the principal ingredient of glass, which has thousands of uses. Silicon, as silicate, is present in pottery, enamels and high-temperature ceramics.

Silicon carbides are important abrasives and are also used in lasers.

Silicon is not known to be toxic, but if breathed in as a fine silica/silicate dust it may cause chronic respiratory problems. Silicates such as asbestos are carcinogenic.

Symbol: Ca Atomic Number: 20 Atomic Weight: 40.08 Calcium (atomic number 20, symbol Ca) is an alkaline earth metal and one of the most abundant elements found in the Earth's crust in terms of mass. This soft gray element is rather hard, and it is important for life on earth, especially for cell physiology whereby the calcium ion Ca2+ moves out and into the cytoplasm, signaling different cellular processes. It is the main component in the mineralization of shells and bones, and the most abundant element of all by mass in many living organisms. Calcium is an important constituent of teeth, leaves, and bones.

Source: Calcium occurs in nature in various minerals including limestone (calcium carbonate), gypsum (calcium sulfate) and fluorite (calcium fluoride). Commercially it can be made by the electrolysis of molten calcium chloride, CaCl2. The pure metal can also be produced by replacing the calcium in lime (CaCO3) with aluminum in hot, low pressure retorts.

Isotopes: Calcium has 19 Isotopes whose half-lives are known, with mass numbers 35 to 53.

Naturally occurring calcium is a mixture of six isotopes and they are found in the percentages shown: 40 Ca (97%), 42Ca (0.6%), 43Ca (0.1%), 44Ca (2%), 46Ca (0.004%) and 48Ca (0.2%).

Calcium is a silvery-white, soft metal that tarnishes rapidly in air and reacts with water.

Calcium is reactive and, for a metal, soft. With a bit of effort, it can be cut with a sharp knife.

In contact with air, calcium develops a mixed oxide and nitride coating, which protects it from further corrosion.

Calcium reacts easily with water and acids and the metal burns brightly in air, forming mainly the nitride.

Calcium metal is used as a reducing agent in preparing other metals such as thorium and uranium. It is also used as an alloying agent for aluminium, beryllium, copper, lead and magnesium alloys.

Calcium compounds are widely used. There are vast deposits of limestone (calcium carbonate) used directly as a building stone and indirectly for cement. When limestone is heated in kilns it gives off carbon dioxide gas leaving behind quicklime (calcium oxide). This reacts vigorously with water to give slaked lime (calcium hydroxide). Slaked lime is used to make cement, as a soil conditioner and in water treatment to reduce acidity, and in the chemicals industry. It is also used in steel making to remove impurities from the molten iron ore. When mixed with sand, slaked lime takes up carbon dioxide from the air and hardens as lime plaster.

Non-toxic and an essential metal for living organisms.

Symbol: Br Atomic Number: 35 Atomic Weight: 79.909 Bromine (atomic number 35, symbol Br) is a chemical element belonging to the halogen group. It is the only nonmetallic, liquid element and a reddish brown, mobile, volatile, and heavy liquid. The vapor irritates the throat and eyes and has an unpleasant, strong odor. Elemental bromine exists in a liquid form at room temperature and is toxic and corrosive. Its properties are similar to those of iodine and chlorine.

Free bromine is not found it nature, and occurs in the form of soluble, colorless, crystalline halide salts.

Source: Bromine is obtained from natural brine deposits. Some bromine is still extracted today from seawater, which contains only about 70 ppm.

Isotopes: Bromine has 26 isotopes whose half-lives are known, with mass numbers 68 to 94.

Naturally occurring bromine is a mixture of its two stable isotopes and they are found in the percentages shown: 79Br (50.7%) and 81Br (49.3%).

Bromine is a deep-red, oily liquid with a sharp smell. It is toxic.

Pure bromine is diatomic, Br2.

Bromine is the only nonmetallic element that is liquid at ordinary temperatures.

It is a dense, reddish-brown liquid which evaporates easily at room temperature to a red vapor with a strong, chlorine-like odor.

Bromine is less reactive than chlorine or fluorine but more reactive than iodine. It forms compounds with many elements and, like chlorine, acts as a bleaching agent.

Bromine is used in many areas such as agricultural chemicals, dyestuffs, insecticides, pharmaceuticals and chemical intermediates. Some uses are being phased out for environmental reasons, but new uses continue to be found.

Bromine compounds can be used as flame retardants. They are added to furniture foam, plastic casings for electronics and textiles to make them less flammable. However, the use of bromine as a flame retardant has been phased out in the USA because of toxicity concerns.

Organobromides are used in halon fire extinguishers that are used to fight fires in places like museums, aeroplanes and tanks. Silver bromide is a chemical used in film photography.

Before leaded fuels were phased out, bromine was used to prepare 1,2-di-bromoethane, which was an anti-knock agent.

Bromine is poisonous and causes skin burns.

Symbol: Co Atomic Number: 27 Atomic Weight: 58.993 Cobalt (symbol Co, number 27) is a chemical element occurring naturally only in a combined compound form. When isolated, it is a silvergray, lustrous, hard metal. It is used quite effectively as a blue pigment and has been used this way since antiquity for jewelry and other decorative items, to give glass a blue tinge, and more. Eventually, it emerged that the metal bismuth had this function. This metal is also known as goblin ore (German) because of the blue color it produced and because it gives off poisonous fumes upon smelting.

Source: Cobalt is not found as a free element in nature. It is found in mineral ores. The main ores of cobalt are cobaltite (CoAsS), erythrite (hydrated arsenate of cobalt), glaucodot (Co,Fe)AsS, and skutterudite (Co,Ni)As3. Cobalt is generally produced as a by-product of nickel and copper mining.

Isotopes: Cobalt has 22 isotopes whose half-lives are known, with mass numbers 50 to 72.

Naturally occurring cobalt consists of its one stable isotope, 59Co.

A lustrous, silvery-blue metal. It is magnetic.

Cobalt is a bluish-white, lustrous, hard, brittle metal. It is ferromagnetic.

The metal is active chemically, forming many compounds. Cobalt stays magnetic to the highest temperature of all the magnetic elements (it has a Curie point of 1121oC).

Cobalt, like iron, can be magnetised and so is used to make magnets. It is alloyed with aluminium and nickel to make particularly powerful magnets.

Other alloys of cobalt are used in jet turbines and gas turbine generators, where high-temperature strength is important.

Cobalt metal is sometimes used in electroplating because of its attractive appearance, hardness and resistance to corrosion.

Cobalt salts have been used for centuries to produce brilliant blue colours in paint, porcelain, glass, pottery and enamels.

Radioactive cobalt-60 is used to treat cancer and, in some countries, to irradiate food to preserve it.

Cobalt and its compounds are considered to be slightly toxic by skin contact and moderately toxic by ingestion.

Symbol: I Atomic Number: 53 Atomic Weight: 126.904 Iodine (atomic number 53, symbol I) is a chemical element with low toxicity, which dissolves easily in chloroform, hexane, and other organic solvents due to its lack of polarity. The color of iodine solutions depends on the solvent and its polarity. Solutions are violet in color in hexane and other non-polar solvents and dark crimson in moderately polar ones. Solutions are brown or orange in strongly polar solvents, for example, ethanol and acetone. When iodine is dissolved in carbon disulphide, carbon tetrachloride, or chloroform, it yields purple-colored solutions. Iodine is slightly soluble in water and gives a yellow solution.

Source: In nature, iodine occurs in the form of iodide ions, mainly in seawater. It is introduced into the food chain via seaweed and other sea-plants. Iodine is found in some minerals and soils.

Commercially, iodine is obtained in several ways, such as taking iodine vapor from processed brine, by ion exchange of brine or by releasing iodine from iodate taken from nitrate ores.

Isotopes: 34 whose half-lives are known, with mass numbers 108 to 141. Naturally occurring iodine consists of the one stable isotope: 127I

A black, shiny, crystalline solid. When heated, iodine sublimes to form a purple vapour.

Iodine is a bluish-black, lustrous solid. Although it is less reactive than the elements above it in group 17 (fluorine, chlorine and bromine) it still forms compounds with many other elements.

Although iodine is a non-metal, it displays some metallic properties.

When dissolved in chloroform, carbon tetrachloride or carbon disulfide, iodine yields purple colored solutions. It is barely soluble in water, giving a yellow solution.

Iodine is important in medicine, in both radioactive and non-radioactive forms. Iodide and thyroxin, which contains iodine, are used inside the body.

A solution containing potassium iodide (KI) and iodine in alcohol is used to disinfect external wounds.

Elemental iodine is also used as a disinfectant.

Silver iodide is used in photography.

Iodine is sometimes added to table salt to prevent thyroid disease.

Iodine’s other uses include catalysts, animal feeds and printing inks and dyes.

In small doses, iodine is slightly toxic and it is highly poisonous in large amounts. Elemental iodine is an irritant which can cause sores on the skin. Iodine vapor causes extreme eye irritation.

Symbol: Pb Atomic Number: 82 Atomic Weight: 207.2 Lead is a chemical element in the carbon group under number 82. Its symbol is Pb, after the Latin plumbum. As we know, in the past, all the plumbing was made of lead, which results in poisoning and death.

Thankfully, it no longer is.

Lead is soft and considered a poor metal, which means that it is a metallic element in the p-block. It is not clear why these elements are considered poor metals. What sets them apart from the others is that their electro-negativity is higher while their melting and boiling points are lower than that of transition metals.

Source: Lead rarely occurs naturally in nature and is can be found in ores, mainly with copper, zinc and silver. The principal lead mineral is lead sulfide (galena, PbS). Other common minerals are cerussite (lead carbonate, PbCO3) and anglesite (lead sulfate, PbSO4). Lead is refined from galena (PbS) by heating. A large amount of lead is also recovered from recycling.

Isotopes: Lead has 35 isotopes whose half-lives are known, mass numbers 181 to 215. Naturally occurring lead is a mixture of four isotopes and they are found in the percentages shown: 204Pb (1.4%), 206Pb (24.1%), 207Pb (22.1%) and 208Pb (52.3%).

A dull, silvery-grey metal. It is soft and easily worked into sheets.

Lead is a bluish-gray, soft, dense metal that has a bright luster when freshly cut.

It tarnishes slowly in moist air to form a dull gray coating.

The metal is highly ductile and malleable.

Lead is extremely resistant to corrosion and is a poor conductor of electricity.

This easily worked and corrosion-resistant metal has been used for pipes, pewter and paint since Roman times. It has also been used in lead glazes for pottery and, in this century, insecticides, hair dyes and as an anti-knocking additive for petrol. All these uses have now been banned, replaced or discouraged as lead is known to be detrimental to health, particularly that of children.

Lead is still widely used for car batteries, pigments, ammunition, cable sheathing, weights for lifting, weight belts for diving, lead crystal glass, radiation protection and in some solders.

It is often used to store corrosive liquids. It is also sometimes used in architecture, for roofing and in stained glass windows.

Lead and its compounds are poisonous.

Symbol: Ti Atomic Number: 22 Atomic Weight: 47.90 Titanium (atomic number 22, symbol Ti) is a transition metal and element from the Periodic Table that was discovered in 1791 by the British mineralogist and clergyman William Gregor who studied Cornish minerals.

Titanium has a silvery-white metallic color, very high strength-to-density ratio, and good corrosion resistance. It is alloyed with different elements, including molybdenum, vanadium, aluminum, iron, and others. At high temperatures, the element reacts with sulfur, silicon, boron, carbon, nitrogen, and other nonmetals. Compounds such as borides, carbide, and nitride have good refractory properties and are hard and stable.

Source: Titanium is the ninth most abundant metal in the Earth’s crust. Titanium is not found freely in nature but is found in minerals such as rutile (titanium oxide), ilmenite (iron titanium oxide) and sphene (titanite or calcium titanium silicate).

Isotopes: Titanium has 18 isotopes whose half-lives are known, with mass numbers 39 to 57.

Naturally occurring titanium is a mixture of its five stable isotopes and they are found in the percentages shown: 46Ti (8.2%), 47Ti (7.4%), 48Ti (73.7%), 49Ti (5.4%) and 50Ti (5.2%). The most naturally abundant of these isotopes is 48Ti at 73.7%.

Pure titanium is a light, silvery-white, hard, lustrous metal. It has excellent strength and corrosion resistance and also has a high strength to weight ratio.

Titanium’s corrosion rate is so low that after 4000 years in seawater, corrosion would only have penetrated the metal to the thickness of a thin sheet of paper. (3) At high temperatures the metal burns in air and, unusually, titanium also burns in pure nitrogen.

Titanium is ductile and is malleable when heated.

It is insoluble in water, but soluble in concentrated acids.

Titanium is as strong as steel but much less dense. It is therefore important as an alloying agent with many metals including aluminium, molybdenum and iron. These alloys are mainly used in aircraft, spacecraft and missiles because of their low density and ability to withstand extremes of temperature.

They are also used in golf clubs, laptops, bicycles and crutches.

Power plant condensers use titanium pipes because of their resistance to corrosion. Because titanium has excellent resistance to corrosion in seawater, it is used in desalination plants and to protect the hulls of ships, submarines and other structures exposed to seawater.

Titanium metal connects well with bone, so it has found surgical applications such as in joint replacements (especially hip joints) and tooth implants.

The largest use of titanium is in the form of titanium(IV) oxide. It is extensively used as a pigment in house paint, artists’ paint, plastics, enamels and paper. It is a bright white pigment with excellent covering power. It is also a good reflector of infrared radiation and so is used in solar observatories where heat causes poor visibility.

Titanium(IV) oxide is used in sunscreens because it prevents UV light from reaching the skin.

Nanoparticles of titanium(IV) oxide appear invisible when applied to the skin.

Titanium metal is considered to be non-toxic. As metal shavings, or powder, it is a considerable fire hazard. Titanium chlorides are corrosive.

Symbol: U Atomic Number: 92 Atomic Weight: 238.03 Uranium (atomic number 92, symbol U) is a metal and chemical element which occurs in nature as three isotopes - U-234, U-235, and U-238. The metal was discovered in 1789 by Martin Klaproth, a German scientist who also isolated cerium and zirconium.

Uranium forms different compounds such as carbonates and oxides, including triuranium octoxide, uranium trioxide and dioxide, and others. Some of the carbonates are water soluble. It reacts with different metals and forms intermetallic compounds, solids, and solutions.

Source: Uranium occurs naturally in several minerals such as uraninite (uranium oxide), carnotite and autunite. Canada is the world’s largest supplier of uranium, producing 20 to 30 percent of supplies. Commercially, uranium is produced through the reduction of uranium halides with alkali earth metals. Although most people think uranium is extraordinarily rare, it is in fact more abundant than familiar elements such as mercury and silver.

Isotopes: Uranium has 21 isotopes whose half-lives are known, with mass numbers 218 to 242.

Natural uranium consists of three major isotopes: 234U, 235U, and 238U. All are radioactive. 238U is the most stable isotope, with a half-life of 4.51 x 109 years (almost the age of the Earth).

Uranium is a dense, silvery-white, slightly paramagnetic, radioactive metal. It is also ductile and malleable. The metal tarnishes in air acquiring a dark layer of oxide. When finely powdered, uranium ignites spontaneously in air.

Uranium is a highly reactive metal and reacts with almost of all the nonmetallic elements and many of their compounds. It dissolves in acids, but it is insoluble in alkalis.

When present in compounds, uranium exists mostly in oxidation state IV and oxidation state VI. All isotopes of uranium are radioactive, some more so than others. Its radioactivity – in particular its capacity to undergo thermonuclear chain reactions – has led to uranium’s use in energy generation, both for civilian and military purposes.

Uranium is a very important element because it provides us with nuclear fuel used to generate electricity in nuclear power stations. It is also the major material from which other synthetic transuranium elements are made.

Naturally occurring uranium consists of 99% uranium-238 and 1% uranium-235. Uranium-235 is the only naturally occurring fissionable fuel (a fuel that can sustain a chain reaction). Uranium fuel used in nuclear reactors is enriched with uranium-235. The chain reaction is carefully controlled using neutron-absorbing materials. The heat generated by the fuel is used to create steam to turn turbines and generate electrical power.

In a breeder reactor uranium-238 captures neutrons and undergoes negative beta decay to become plutonium-239. This synthetic, fissionable element can also sustain a chain reaction.

Uranium is also used by the military to power nuclear submarines and in nuclear weapons.

Depleted uranium is uranium that has much less uranium-235 than natural uranium. It is considerably less radioactive than natural uranium. It is a dense metal that can be used as ballast for ships and counterweights for aircraft. It is also used in ammunition and armour.

Uranium is harmful both through its chemical toxicity and its radioactivity. Exposure to uranium increases your risk of getting a variety of cancers due to its radioactivity.

CONCLUSION

What we can conclude about this activity is that all the elements independent of the corresponding group, the period, atomic number, or age, all of them helps us pretty much, although many of them are toxic. But most of them help us and contribute by an extremely and incredible way.

If the elements exist in the world is because a determined cause, a purpose: benefit the world, benefit the people and make the complex world an easier world.

In this activity we show you some chosen elements: Li, C, Si, Ca, Br, Co, I, Pb, Ti and U; all of those symbols show mainly their atomic number, their name (of the element); each element shows his general description, their isotopes, etc. Then shows by a periodic table’s image his location. His chemical and physical properties, applications and uses, and if the element perjuries the people or not by some natural effect.

RESOURCES:

http://www.chemicool.com/elements/uranium.html http://www.chemicool.com/elements/titanium.html http://www.rsc.org/periodic-table/element/22/titanium http://www.chemicool.com/elements/lead.html http://www.chemicool.com/elements/iodine.html http://www.elementsdatabase.com/Lithium-Li-3-element/ http://chemistry.about.com/od/chemistryfaqs/f/element.htm http://chemistry.about.com/od/chemicalcomposition/f/What-IsThe-Moon-Made-Of.htm https://www.quora.com/What-are-importance-of-elements http://www.answers.com/Q/What_is_the_importance_of_elements_in _life?#slide=2 http://www.ptable.com/?lang=es http://pmm.umicore.com/en/prices/palladium/ http://elements.wlonk.com/ElementUses.htm http://www.elementalmatter.info/periodic-table-chart.htm