Mo
MOLYBDENUM
( Gr. molybdos, lead)
Mo at. wt. 95.94
at. no. 42
m.p. 2610°C
b.p. 5560°C
sp. gr. 10.22 (20°C)
valence 2, 3, 4?, 5?, or 6.
Electronic configuration
| SHELL |
K |
L |
M |
N |
O |
P |
Q |
| SUB SHELL |
He |
Neon |
Argon |
Krypton |
Xenon |
Radon |
Eka-radon |
| 1s |
2s 2p |
3s 3p |
3d 4s 4p |
4d 5s 5p |
4f 5d 6s 6p |
5f 6d 7s 7p |
| Molybdenum
|
1s22s22p63s23p63d104s24p64d55s1 |
|
|
| Symbol
|
7S3 |
Molybdenum was confused with graphite and lead ore before Scheele recognized molybdenite as a distinct ore of a new element in 1778. The metal was prepared
in an impure form in 1782 by Hjelm. Molybdenum does not
occur native, but is obtained principally from molybdenite
(MoS2). Wulfinite (PbMoO4) and powellite (Ca(MoW)04)
are also minor commercial ores. Molybdenum is also re-
covered as a byproduct of copper and tungsten mining
operations. The metal is prepared from the powder made
by the hydrogen reduction of purified molybdic trioxide or
ammonium molybdate. The metal is silvery white, very hard,
but is softer and more ductile than tungsten. It has a high
elastic modulus, and only tungsten and tantalum, of the
more readily available metals, have high melting points. It is
a valuable alloying agent, as it contributes to the harden-
ability and toughness of quenched and tempered steels. It
also improves the strength of steel at high temperatures. It is
used in certain nickel-based alloys, such as the "Hastelloys,"
which are heat-resistant and corrosion-resistant to chemical
solutions. Molybdenum oxidizes at elevated temperatures.
The metal has found recent application as electrodes for
electrically heated glass furnaces and forehearths. The metal
is also used in nuclear energy applications and for missile and
aircraft parts. Molybdenum wire is valuable for use as a
filament material for metal evaporation work, and as a fil-
ament, grid, and screen material for electronic tubes. Molyb-
denum is an essential trace element in plant nutrition. Some
lands are barren for lack of this element in the soil. Molyb-
denum sulfide is useful as a lubricant, especially at high
temperatures where oils would decompose. Almost all ultra-
high strength steels with minimum yield points up to 300,000
psi (lb./sq. in.) contain molybdenum in amounts from 0.25%
to 8%. Molybdenum powder is priced at about $4/lb., and
bars rolled from arccast ingots cost about $15/lb.
© 1999 F. Davies
Delphi O.E.M. Co.
All rights reserved
