IRON
Symbol : Fe
Latin name : Ferrum
Atomic number : 26
Atomic mass : 55.86
Valency : 2 and 3
Electronic configuration : 1s2,2s22p6, 3s2 3p63d6, 4s2
Introduction
Iron has been known since prehistoric times and no other element has played a more important role in human's material progress than iron. The symbol Fe is derived from the Latin ferrum for iron. Biologically, iron plays crucial roles in the transport and storage of oxygen and also in electron transfer. With few exceptions, it will be safest to quote that there would be no life without oxygen and iron. Deficiency of iron in humans "causes anaemia i.e. loss of blood. The adult human body contains about 4 g of iron, of which 39
are in the form of haemoglobin, and this level is maintained by absorbing just 1 mg of iron per day. ~ '
The famous bridge at Ironbn‘dge in Shropshire England marks a historic industrial revolution in Europe. Made from cast iron, it was the first iron bridge in the world which was opened in 1781. The metal iron is a transition element. We use about nine nines more iron than all the other metals put together. Modern bridges such as the Forth road bridge in Scotland are now made of steel, where iron is alloyed with other transition elements and carbon to make it stronger.
Occurrence
Iron is the fourth most abundant element in the earth crust. Due to its high reactivity, it rarely occurs in free state. The important ores of iron are:
a. Haematite: Fe203
b. Magnetite: Fe304
c. Iron pyrite: FeS2
d.Brown haematite or Iimonite: Fe203.3H2O
e.Siderite or spathic ore: FeCO3
Small quantity of iron is also present in clay, green leaves of the plant and haemoglobin of the human blood. Iron pyrite contains 40% of iron but is not used as the source of iron due to the presence of excess of sulphur. Iron so obtained from iron pyrite is costly and brittle' This ore of iron is used in the manufacture of sulphuric acid and sulphur dioxide.