Group VIB; Chromium Group

Chromium (Cr), molybdenunm (Mo) and tungsten (W) are rather important elements .
Chromium is the key ingredient for stainles steels; it is also indispensable for many other prodcuts and applications. A few million tons are produced every year; no more needs to be said.
Molybdenunm (Mo) and tungsten (W) have very high metling points asn are thus indispensable for high temperature applications (e.g. the tungsten filament in your light bulb). Both are used as alloying element in steel (and in other alloys).
You very likely have Molybdenum silicide (MoSi2) in you household, It is usually the heating element in dishwashers or washing machines since it has the right specific resistivity and, most important, does not corrode in these extremely harsh environments.
Table of Basic Data
Atomic number 24 42 74
Atomic mass [u ] 51,9961 95,94 183,85
Melting point [K] 2130 2890 3680
Melting point [oC] 1857 2617 3407
Melting point [oF] 3375 4742 6165
Boiling point [K] 2755 5833 6200
Density [g/cm3] 7,14 10,28 19,26
Ionization energy [eV] 6,766 7,099 7,98
Electro-negativitiy 1,6 1,3 1,4
Atomic radius [pm] 124,9 136,2 137,0
Ionic radius [pm] 64 62 62
Oxidation numbers 6 to -2 6 to -2 6 to -2
Lattice typ
Transformation temp. [oC]
Lattice constant [Å]
(a or c)
2,89 3,15 3,16
Young's - Modul us [GPa] 186 301 388
Therm. expansion coefficient a
[10-6K -1]
? 6,5 7,0
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)