H' at. wt. (natural) 1.007967
at. wt. (H') 1.007822
at. no. 1
m.p. - 259.140C
b.p. - 252.870C
density 0.08988 gm./l
density (liquid) 70.8 gm/i. (-2530C)
density (solid) 7016 gm/i. (-2620C)
valence 1.
Electronic configuration
| K |
L |
M |
N |
O |
P |
Q |
| 1 |
2 |
3 |
4 |
5 |
6 |
7 |
| s |
s p |
s p d |
s p d f |
s p d f |
s p d f |
s p d f |
| 1 |
|
|
|
|
|
|
HAFNIUM (Hafnia, Latin name for Copenhagen), Hf;
at. wt. 178.49; at. no.72; m.p. 21500C; b.p. 54000C; sp. gr.
13.31 (200C); valence 4. Hafnium was thought to be
present in various minerals and concentrations many years
prior to its discovery, in 1923, credited to D. Coster and
G. von Hevesey. On the basis of the Bohr theory, the new
element was expected to be associated with zirconium. It
was finally identified in zircon from Norway, by means of
X-ray spectroscopk analysis. It was named in honor of the
city in which the discovery was made. Most zirconium
minerals contain 1 to 5 % hafnium. It was originally
B-15
separated from zirconium by repeated recrystallization of
the double ammonium or potassium fluorides by v~p
Hevesey and Jantzen. Metallic hafnium was first prepared
by van Arkel and deBoer by passing the vapor of the tetra-
iodide over a heated tungsten filament. Almost all hafnium
metal now produced is made by reducing the tetrachloride
with tnagnesium or with sodium (Kroll Process). Hafnium
is a ductile metal with a brilliant silver luster. Its properties
are considerably influenced by the impurities of zirconium
present. Of all the elements, zirconium and hafnium are the
two of the most difficult to separate. Their chemistry is
almost identical; however the density of zirconium is about
half that of hafnium. Very pure hafnium has been produced
with zirconium being the major impurity. Because hafnium
has a good absorption cross-section for thermal neutrons
(almost 600 times that of zirconium), has excellent mechani-
cal properties, and is extremely corrosion resistant, it is
used for reactor control rods. Such rods are used in nuclear
submarines. Hafnium has been successfully alloyed with
iron, titanium, niobium, tantalum, a~d other metals.
Hafnium carbide is the most refractory binary composition
known, and the nitride is the most refractory of all known
metal nitrides (m.p. 33100C). Hafnium is used in gas-filled
and incandescent lamps, and is an efficient "getter" for
scavenging oxygen and nitrogen. Finely divided hafnium
is pyrophoric and can ignite spontaneously in air. Care
should be taken when machining the metal or when handlin'g
hot sponge hafnium. At 7000C hafnium rapidly absorbs
hydrogen to form the composition HfH1,86. Hafnium is
resistant to concentrated alkalis, but at elevated tempera-
tures reacts with oxygen, nitrogen, carbon, boron, sulfur, and
silicon. Halogens react directly to form tetrahalides. The
price of the metal is in the broad range of $30 to $175/lb.,
depending on puyity and quantity. The yearly demand for
hafnium in the U.S. is now in excess of 60,000 lbs.
© 1999 F. Davies
Delphi O.E.M. Co.
All rights reserved
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