Iron PDF

Iron Iron is a chemical element; it has symbol Fe (from Latin ferrum 'iron') and atomic number 26. It i...

Iron Iron is a chemical element; it has symbol Fe (from Latin ferrum 'iron') and atomic number 26. It is a metal that belongs to the first transition series and group8 of the periodic tabe. It by mass, is, common element on Earth,forming much of Earth's outer and inner core. It is the fourth the most most common element in the Earth's crust, being mainly depositedby meteorites in its metallic state. Extracting usable metal from iron ores requires kilns or furnaces capable of reaching 1,500 °C (2,730 °F), about 500C (932 °F) higher than that required to smelt copper. Humans started to Eurasia during the 2nd millennium BC and the use of master that process in iron tools and weaponsbegan to displace copper alloys -insome regions,only around 1200 BC. That event is considered the transition from the Bronze Age to the Iron Age. In the modern world, alloys, such as steel, stainless steel, cast iron and special steels, are by far the most common iron metals, due totheir mechanical properties and low cost. The iron and steel industry is thus industrial the cheapest metal, with a price of a few dollars per very important economically, and iron is kilogramn or pound. Iron reacts readily with oxygen Pristine and smooth pure iron surfacesare a mirror-ike silvery-gray. and water to produce brown-to-black hydrated iron. oxides,commonly known as rust. Unlike the some other metals that form passivating layers, rust occupies more volume than the metal Oxides of more fresh surfaces for corrosion.Chemically, the mostcommon and thus flakes off, exposing shares many properties other transition iron are iron(l) and iron(l). Iron of oxidation states of metals, iincluding the other group 8 elements, ruthenium and osmium. Iron forms compounds in a wide range of oxidation states, -4to +7. Iron also forms many coordination compounds; some of and Prussian blue have substantial industrial, medical, or them, such as ferrocene, ferrioxalate, research applications. The body of an adult human contains about 4 grams(0.005% body weight) of iron, mostly in hemoglobin and myoglobin.These two proteins play essential roles in oxygen necessary levels, human iron transport by blood and oxygen storage in muscles. To maintain the metabolism requires a minimum of iron in the diet. Iron is also the metal at the active site of many important redox enzymes dealing with cellular respiration and oxidation and reductíon in plants and animals. Characteristics Allotropes Main article: Allotropes of iron Expisse 161.77 Ca K 4 Molar volume vs. pressure for a iron at room temperature At least four allotropes of iron (differing atom arrangements in the solid) are known, conventionally denoted a, y, 6, and. Thefirst three forms are observed at ordinary pressures.As molten iron cools past its-freezing point of 1538 c, it crystallizes into its 6 allotrope, which has a body-centered cubic (bcc)crystal structure. As it cools furtherto 1394 °C, it changes to its y-iron allotrope, a face-centered cubic (fcc) crystal structure,or austenite.At 912 °C and below, the crystal structure again becomesthe bcc a-iron allotrope. [10) The physical properties of iron at very high pressures and temperatures have also been studied extensively, [11}{12]because of their relevance to theories about the cores of theEarth and other planets. Above approximately 10 GPa and temperatures of a few hundred kelvin or less, a-iron changes into another hexagonal close-packed (hcp) structure,which is also known as E-iron. The higher-temperature y-phase also changes into -iron, but does soat higher pressure. Some controversial experimental evidence exists for a stable B phase at pressures above50 GPa and temperatures of at least 1500 K. It is supposed to have an orthorhombic or a double hcp (Confusingly,the term "B-iron" is sometimes also used to refer to a-iron structure. aboveits Curie point,when it changes from being ferromagnetic to paramagnetic, even though its crystal structure has not changed.) The inner core of the Earth is generally presumed to consist of an iron-nickel alloy with (or B) structure. Melting and boiling points 3030 2500 2000 - 1500 130 10* 10 13 10* 1 Low-pressure phase diagram of pure iron The melting and boiling points of iron, along with its enthalpy of atomization, are lower than those of the earlier 3d elements from scandium to chromium, showing the lessened contribution of the 3d electrons to metallic bonding as they are attracted more and more into the inert core by the nucleus;15] however, they are higher than the values for the previous element manganese because that element has a half-filled 3d sub-shelland consequently its d-electrons are not easily delocalized. This same trend appears for ruthenium but not osmium.(16} The melting point of iron is experimentally well defined for pressures less than 50 GPa.. For greater pressures, published data (as of 2007) still varies by tens of gigapascals and over a thousand kelvin.[17} Magnetic properties  2.0 1.8 l.6 tesla B field. 0.8 0.6 0.4 0.2 20 40 60 80 100120 140 160 materials, 0 /inch of 9 ferromagnetic H field, ampeeturns Magnetizationcurves 5. Magnet steel, steel, steel, 4. Tungsten 2. Silicon steel, 3.Cast 1. Sheet steel, showing saturation. 8.Cobalt, 9. Magnetite 6. Cast iron, 7. Nickel, changes (1,420F; 1,040 K), a-iron 770 °C each atom generally Below Curie point of electrons in spins of thetwo unpaired its ferromagnetic: the the happens because from paramagneticto an overall magnetic field. This creating spins of its neighbors, atoms in the lattice, align with the not point toward neighboring two electrons (d and d'-) do orbitals of those involved in metallic bonding.10] and therefore are not partitioned the atoms get spontaneously of an external source of magnetic field, in each domain have In the absence across,20] such that the atoms about 10 micrometers of iron will have into magnetic do9ains, Thusa macroscopic piece domains have other orientations. parallel spins, but some zero overall magnetic field. a nearly in the same domains that are magnetized magnetic field causes the of an external reinforcing Application point in other directions, at expense of adjacentones that generaldirection to grow the fields to fulfill in devices that need to channel magnetic field. This effect is exploited the external and electric motors. as electrical transformers, magnetic recording heads, such new design function, particle boundaries can "pin" thedomains in the defects, or grain and turning the iron Impurities, lattice is removed-thus persists even after the external field positions, so that the effect into a (permanent) magnet. object including the exhibited by some iron compounds, such as the ferrites Similar behavior oxide Fe304 (althoughthe atomic-scale is form of the mixed iron(|I,1I) mineralmagnetite, a crystalline magnetite with natural permanent somewhat different). Pieces of mechanism, ferrimagnetism, is of magnetite theearliest compasses for navigation. Particles magnetization(ladestanes) provided tapes, floppies, such as core memories, magnetic were extensively used in magnetic recording media by cobalt-based materials. and disks, until they were replaced