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Atomic Number: 26
Atomic Symbol: Fe
Atomic Weight: 55.847
Electron Configuration: [Ar]4s23d6
History
(Anglo-Saxon, iron; L. ferrum) Iron was used prehistorically. A
remarkable iron pillar, dating to about A.D. 400, remains standing today in
Delhi, India. This solid shaft of wrought iron is about 7 1/4 m high by 40 cm in
diameter. Corrosion to the pillar has been minimal although it has been exposed
to the weather since its erection.
Sources
Iron is a relatively abundant element in the universe. It is found in
the sun and many types of stars in considerable quantity. Its nuclei are very
stable. Iron is a principal component of a meteorite class known as siderites
and is a minor constituent of the other two meteorite classes. The core of
the earth -- 2150 miles in radius -- is thought to be largely composed of iron
with about 10 percent occluded hydrogen. The metal is the fourth most abundant
element, by weight that makes up the crust of the earth.
The most common ore is hematite, which is frequently seen as
black sands along beaches and banks of streams.
Isotopes
Common irons is a mixture of four isotopes. Ten other isotopes are
known to exist.
Uses
Iron is a vital constituent of plant and animal life and appears in
hemoglobin.
Taconite is becoming increasingly important as a commercial ore.
The pure metal is not often encountered in commerce, but is usually alloyed with
carbon or other metals.
Properties
The pure metal is very reactive chemically and rapidly corrodes,
especially in moist air or at elevated temperatures. It has four allotropic
forms or ferrites, known as alpha, beta, gamma, and omega, with transition
points at 700, 928, and 1530C. The alpha form is magnetic, but when transformed
into the beta form, the magnetism disappears although the lattice remains
unchanged. The relations of these forms are peculiar. Pig iron is an alloy
containing about 3 percent carbon with varying amounts of
Sulfur, Silicon,
Manganese, and Phosphorus.
Iron is hard, brittle, fairly fusible, and is used to produce
other alloys, including steel. Wrought iron contains only a few tenths of a
percent of carbon, is tough, malleable, less
fusible, and has usually a "fibrous" structure.
Carbon steel is an alloy of iron with small amounts of Mn, S, P,
and Si. Alloy steels are carbon steels with other additives such as
nickel, chromium,
vanadium, etc. Iron is a cheap, abundant, useful,
and important metal.
Sources: CRC Handbook of Chemistry and
Physics and the American Chemical Society.
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