Iron, ruthenium and osmium, situated in group 8 of the periodic table, are silvery, shiny metals. As is the case with many of the transition element triads, resemblances between the second and third group members are more striking than those that exist between all three.
Whereas ruthenium and osmium are hard metals, and are used as hardening agents in alloys, iron is relatively soft. It is also easier to work.
Iron is also more reactive than the other two. It combines readily with most of the non-metallic elements - the halogens, sulphur, chlorine, phosphorus and silicon - whereas ruthenium and osmium do so only at high temperatures, and then with some difficulty. Iron dissolves in most dilute acids, whereas ruthenium and osmium are widely resistant to acidic attack, even from the extremely powerful aqua regia. The latter two elements are also resistant to oxidation on exposure to air, whereas iron reacts with atmospheric oxygen to form hydrated iron oxide, commonly known as rust.
Osmium is much denser than the other two elements, and, indeed, of all the chemical elements, is second only to iridium in terms of density.
Iron is ferromagnetic up to a temperature of 768 degrees Celsius.
