Hafnium tetrafluoride

Hafnium tetrafluoride is the inorganic compound with the formula HfF4. It is a white solid. It adopts the same structure as zirconium tetrafluoride, with 8-coordinate Hf(IV) centers.

Hafnium(IV) fluoride
Zirconium(IV) fluoride
Names
IUPAC names
Hafnium(IV) fluoride
Hafnium tetrafluoride
Identifiers
ECHA InfoCard 100.033.856
Properties
HfF4
Appearance white crystalline powder
Density 7.1 g/cm3[1]
Boiling point 970 °C (1,780 °F; 1,240 K) (sublimes)[1]
Structure
Monoclinic, mS60[2]
C2/c, No. 15
a = 1.17 nm, b = 0.986 nm, c = 0.764 nm
Hazards
Flash point Non-flammable
Related compounds
Other anions
Hafnium(IV) chloride
Other cations
Titanium(IV) fluoride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

References

  1. ^ a b Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nd ed.). Boca Raton, FL: CRC Press. p. 4.66. ISBN 1439855110.
  2. ^ Zachariasen, W. H. (1949). "Crystal chemical studies of the 5f-series of elements. XII. New compounds representing known structure types". Acta Crystallographica. 2 (6): 388. doi:10.1107/S0365110X49001016.

Further reading

  • Benjamin, S. L., Levason, W., Pugh, D., Reid, G., Zhang, W., "Preparation and structures of coordination complexes of the very hard Lewis acids ZrF4 and HfF4", Dalton Transactions 2012, 41, 12548. doi:10.1039/C2DT31501G
Compounds of thorium

Many compounds of thorium are known: this is because thorium and uranium are the most stable and accessible actinides and are the only actinides that can be studied safely and legally in bulk in a normal laboratory. As such, they have the best-known chemistry of the actinides, along with that of plutonium, as the self-heating and radiation from them is not enough to cause radiolysis of chemical bonds as it is for the other actinides. While the later actinides from americium onwards are predominantly trivalent and behave more similarly to the corresponding lanthanides, as one would expect from periodic trends, the early actinides up to plutonium (thus including thorium and uranium) have relativistically destabilised and hence delocalised 5f and 6d electrons that participate in chemistry in a similar way to the early transition metals of group 3 through 8: thus, all their valence electrons can participate in chemical reactions, although this is not common for neptunium and plutonium.

Hafnium tetrachloride

Hafnium(IV) chloride is the inorganic compound with the formula HfCl4. This colourless solid is the precursor to most hafnium organometallic compounds. It has a variety of highly specialized applications, mainly in materials science and as a catalyst.

Tetrafluoride

A tetrafluoride is a chemical compound with four fluorines in its formula.

Thorium

Thorium is a weakly radioactive metallic chemical element with symbol Th and atomic number 90. Thorium is silvery and tarnishes black when it is exposed to air, forming thorium dioxide; it is moderately hard, malleable, and has a high melting point. Thorium is an electropositive actinide whose chemistry is dominated by the +4 oxidation state; it is quite reactive and can ignite in air when finely divided.

All known thorium isotopes are unstable. The most stable isotope, 232Th, has a half-life of 14.05 billion years, or about the age of the universe; it decays very slowly via alpha decay, starting a decay chain named the thorium series that ends at stable 208Pb. In the universe, thorium and uranium are the only two radioactive elements that still occur naturally in large quantities as primordial elements. It is estimated to be over three times as abundant as uranium in the Earth's crust, and is chiefly refined from monazite sands as a by-product of extracting rare-earth metals.

Thorium was discovered in 1829 by the Norwegian amateur mineralogist Morten Thrane Esmark and identified by the Swedish chemist Jöns Jacob Berzelius, who named it after Thor, the Norse god of thunder. Its first applications were developed in the late 19th century. Thorium's radioactivity was widely acknowledged during the first decades of the 20th century. In the second half of the century, thorium was replaced in many uses due to concerns about its radioactivity.

Thorium is still being used as an alloying element in TIG welding electrodes but is slowly being replaced in the field with different compositions. It was also a material in high-end optics and scientific instrumentation, and as the light source in gas mantles, but these uses have become marginal. It has been suggested as a replacement for uranium as nuclear fuel in nuclear reactors, and several thorium reactors have been built.

This page is based on a Wikipedia article written by authors (here).
Text is available under the CC BY-SA 3.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.