Iron, one of the transition metals, is a common and well known element. Most readers will be familiar with it as a dull gray metal, great for making nails, horseshoes, and skillets. It is one of the stronger metals, and has a higher melting temperature than copper (or its alloy, bronze), which is why the Iron Age was a long time in coming. Hotter fires were required to smelt (extract the iron from the ore) and work the iron into useful forms.
Strong as it is, iron can be strengthened further by mixing it with other elements to form alloys referred to as steel. Mixed with carbon, you get carbon steel. Other properties can be gained by alloying iron as well. Chromium and/or nickel are usually found in “stainless” steels, giving it a superior resistance to oxidation.
The tendency of iron to rust (be oxidized) is a well-known facet of iron. Less well-known, perhaps, is that iron rust (Fe2O3) in a fine, pure powder makes an excellent red colorant that can be used in foods, cosmetics, drugs, or art. This red iron rust is sometimes called “ferric oxide”. Another form of oxidized iron, FeO, has a yellow color (also used as a colorant) and is called “ferrous oxide”. Noting the similarity between the names, it isn’t surprising to most people to learn that in Latin, the name for iron is ferrum. It is from this name that iron gets its chemical symbol – Fe.
Another commonly known property of iron is that it is attracted by magnets, and can even be temporarily magnetized itself. Ferromagnetism (notice that prefix again) results from its special configuration of unpaired electrons that gives each atom a small magnetic field. When placed in in the field of a magnet, the atoms align themselves with the field, causing a magnetic attraction. Given a strong enough magnetic field, the alignment lasts for a while, and the iron – be it a nail, bar, or sculpture – is said to be magnetized. Heat or impacts will cause the atoms to resume random alignments in time, so the magnetism is not permanent.
Iron is an important element in the body. It is the central atom in hemoglobin – the compound in red blood cells that is responsible for oxygen transport throughout the body. Similarly, iron is a part of other enzymes in the body. When a person doesn’t have enough iron in their diet (or an illness prevents them from absorbing it), their body cannot function properly, and they get sick (or sicker). Iron deficiencies can be fatal. Of course, too much of a good thing can be just as bad. Iron is a heavy metal, and too much of it is toxic to the body. Foods and drugs are carefully monitored for iron content, so there is a very limited risk of overexposure to iron in today’s society.
Physical and Chemical Data:*
Iron (Fe) is element number 26. It has 26 protons, 26 electrons, and comes in four isotopic forms, having 28 (5.8%), 30 (91.8%), 31 (2.1%), and 32 (0.3%) neutrons, respectively.
The average atomic mass of iron is 55.845 amu.
Iron melts at 1538 degrees Celsius. It will even boil if heated to 2861 degrees Celsius. (Gaseous iron can be found in stars.)
The density of iron is 7.87 g/cc. (That’s slightly lighter than copper, which had a density of 8.96 g/cc, and lighter on average than bronze, which ranges from 7.4 g/cc to 8.9 g/cc depending how much tin is in the alloy*. Either way, that harder, lighter iron/steel sword had a massive advantage.)
Iron’s electron configuration is: 1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d6 or, for lazy folk like me, [Ar] 4s2, 3p6.
Iron can form a variety of oxidation states, but only the +2 (ferrous) and +3 (ferric) ions are commonly seen in nature. In the lab, the application of an electric potential makes it easy to generate the +1, +4 or even +5 species. (Outside of highly specialized research, you probably don’t care about that.)
*Most numerical data retrieved from the 82nd edition of the CRC Handbook of Chemistry and Physics. (Some I already knew, but the CRC can have that credit too.)
*Density of bronze found at http://www.simetric.co.uk/si_metals.htm