Hafnium atomic properties

Ordering the elements in the periodic table known at that time according to their atomic numbers instead of atomic weights gave the same order that Mendeleev had decided must be true in order for elements with similar properties to fall into the same columns. Even more importantly, however, before Moseley s work no one knew how many elements there should be with atomic weights between those of lanthanum and hafnium (the so-called lanthanides). By assigning lanthanum atomic number 57 and hafnium atomic number 72, it became clear that there should be fourteen lanthanides. Since thirteen lanthanides were... 

K. L. Komarek, ed.. Hafnium Physico-Chemical Properties of Its Compounds andEUhys, International Atomic Energy Agency, Vieima, 1981, pp. 11,13,14, 16. Covers tbermocbemical properties, phase diagrams, crystal stmcture, and density data on hafnium, hafnium compounds, and alloys. 

The effect of the lanthanide contraction on the metal and ionic radii of hafnium has already been mentioned. That these radii are virtually identical for zirconium and hafnium has the result that the ratio of their densities, like that of their atomic weights, is very close to Zr Hf = 1 2.0. Indeed, the densities, the transition temperatures and the neutron-absorbing abilities are the only common properties of these two elements which differ... 

Generally, for the chemical engineer not particularly associated with atomic energy, unalloyed zirconium containing hafnium is an appropriate choice for those occasions which require the special corrosion resistant properties exhibited by the metal. 

Georg von Hevesy. Hungarian chemist who, with Dr. Dirk Coster of the University of Groningen, discovered the element hafnium in zirconium ores and made a thorough study of its properties. Author of many papers on chemical analysis by X-rays, radioactivity, the rare earths, and electrolytic conduction. In 1943 he was awarded the Nobel Prize in Chemistry and in 1959 he received the Atoms for Peace Award. 

Zirconium and hafnium possess nearly identical chemistry. No other pair of congeners has chemical properties so similar to each other. This is mostly a result of the metals possessing nearly identical atomic and ionic radii (1.45 and 1.44 A for Zr and Hf, and 0.86 and 0.85 A for Zi + and Hf +) as a resnlt of the lanthanide contraction. They are relatively electropositive, but less so than the group 3 metals. The metals themselves... 

Another effect of lanthanide contraction is that the third row of the d-block elements have only marginally larger atomic radii than the second transition series. For example, zirconium and hafnium, niobium and tantalum, or tungsten and molybdenum have similar ionic radii and chemical properties (Zr + 80 pm, Hf + 81 pm Nb + 70 pm, Ta + 73 pm Mo + 62 pm, W + 65 pm). These elements are also found in the same natural minerals and are difficult to separate. 

After helium and argon had been discovered the existence of neon, krypton, xenon, and radon was clearly indicated by the periodic law, and the search for these elements in air led to the discovery of the first three of them radon was then discovered during the investigation of the properties of radium and other radioactive substances. While studying the relation between atomic structure and the periodic law Niels Bohr pointed out that element 72 would be expected to be similar in its properties to zirconium. G. von Hevesy and D. Coster were led by this observation to examine ores of zirconium and to discover the missing element which they named hafnium. 

The physical property of greatest interest for hafnium is how it responds to neutrons. A neutron is a very small particle found in the nucleus (center) of an atom. Neutrons are used to make nuclear fission reactions occur. Nuclear fission reactions take place when a neutron strikes a large atom, such as an atom of uranium. The neutron makes the atom break apart. In the process, a large amount of energy is released. That energy can be converted to electricity. 

Cdtium was isolated from the soluble end of a series from gadolinite by fractional crystallization of the nitrates in nitric add. Its compounds have properties intermediate between those of scandium and lutecium. Its atomic weight has not been determined, but the atomic number 72 has been assigned to this element. The discovery of hafnium, a close relative of... 

All these new discoveries, of course, verified Seaborg s theory, and the transuranium elements, along with thorium, protactinium and uranium, are now called the actinide elements. They all fit in the Periodic Table between actinium and the element eka-hafnium. Eka-hafnium is the tentative name given to the undiscovered element with the atomic number 104 which lies directly below hafnium in the Periodic Table and which is expected to have chemical properties similar to those of hafnium. 

The elements will be discussed in the order of increasing atomic number in the Periodic Table, i.e. nickel, zinc, technetium, ruthenium, silver, hafnium, tantalum, tungsten, rhem um, osmium, iridium, platinum, gold, and mercury. Full numerical data of the relevant nuclear properties are summarized, as for other elements, in Appendix 1. 

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