Group 8 - 10 / VIIIB; Iron - Platinum Group

The Iron - Platinum Group is often subdivided into the iron group proper (group 8) containing iron (Fe), cobalt (Co) and nickel (Ni), and the platinum group with ruthenium (Ru), rhodium (Rh), palladium (Pd), Osmium (Os), iridium (Ir) and platinum (Pt). Here we treat them in one module.
Nothing need to be said about the importance of iron. Nickel is not only an important alloy element in steel (in particular in stainless steels) but in the base element for what are called "super-alloys", indispensable materials for high-temperature applications like in jet turbines. Cobalt also has many applications of its own.
Iron, nickel and cobalt are are the only elements that are ferromagnetic at reasonable temperatures and thus often found in magnetic (and thus also electric) machinery and products.
The platinum group elements are all more or less noble metals, rare and expensive. Besides being used in jewelry, platinum is of extreme technical importance as a kind of universal catalyst for all kind of processes. It is part of the exhaust clean-up system of your present car and will be part of the fuel cells that power (perhaps) the cars of the future. Palladium also finds unique and substantial technical uses.
Table of Basic Data
 
Name
(German)
Iron
Eisen
Cobalt
Cobalt
Nickel
Nickel
Ruthenium
Ruthenium
Rhodium
Rhodium
Palladium
Palladium
Osmium
Osmium
Iridium
Iridium
Platinum
Platin
Atomic number 26 27 28 44 45 46 76 77 78
Atomic mass [u] 55,85 58,93 58,69 101,07 102,91 106,42 190,2 192,22 195,08
Melting point [K] 1808 1768 1726 2583 2239 1825 3318 2683 2045
Melting point [oC] 1535 1495 1453 2310 1966 1552 3045 2410 1772
Melting point [oF] 2795 2723 2647 4190 3625 2825 5513 4370 3221
Boiling point [K] 3023 3143 3005 4173 4000 3413 4300 4403 4100
Density [g/cm3] 7,87 8,89 8,91 12,45 12,41 12,02 22,61 22,65 21,45
Ionization energy [eV] 7,87 7,86 7,64 7,37 7,46 8,34 8,7 9,1 9,0
Electronegativitiy 1,6 1,7 1,8 1,4 1,5 1,4 1,5 1,6 1,4
Atomic radius [pm] 124,1 125,3 124,6 134 134,5 137,6 135 135,7 138
Ionic radius [pm] 67 82 78 77 75 86 67 66 85
Oxidation numbers 6 bis -2 5 bis -1 4 bis -1 8 bis -2 6 bis -1 4 bis 2 8 bis -2 6 bis -1 6 bis 2
Lattice typ
Transformation temp. [oC]
bcc
1402
fcc
910
bcc
fcc
440
hcp
fcc
hcp
fcc
fcc
hcp
fcc
fcc
?
Lattice constant [Å]
(a or c)
2,86 2,51
4,07
3,52 2,70
4,27
3,80 3,88 2,73
4,31
3,83 3,92
Young's - Modul us [GPa] 213 204 202 (432) 379 113 560 528 168
Therm. expansion coefficient a
[10-6K-1]
14,0 12,0 12,5 9,8 8,5 11,2 ? 6,6 8,94
 
In case of doubt all numbers are for room temperatures
fcc = face centered cubic; lattice const. = a
bcc = body centered cubic
sc = simple cubic
hp = simple hexagonal
hcp = hexagonal close packed; lattice constants a and c.
op = simple orthorhombic, monoclinic, triclinic
tp = simple tetragonal
dia = diamond structure
r = trigonal or rhomboedral trigonal


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© H. Föll (Iron, Steel and Swords script)