Kurchatovium

kurchatovium (kûr'chətō`vēəm), symbol Ku, former suggested name for element 104, now called rutherfordium.

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kurchatovium [‚kər·chə′tō·vē·əm]

(chemistry)

The name suggested by workers in the Soviet Union for element 104. Symbolized Ku.

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Kurchatovium 

Ku, an artificially produced radioactive element of group IV of the Mendeleev periodic table; atomic number, 104. The only known isotopes of kurchatovium are radioactive: ²⁶⁰Ku and ²⁵⁹Ku (with half-lives of 0.1 and 4.5 sec), first discovered in Dubna (USSR) in 1964 and 1966 by spontaneous nuclear fission, and ²⁶¹Ku and ²⁵⁷Ku (T½ = 4.5 and 65 sec), first recorded in Berkeley (USA) by alpha emission.

Kurchatovium was synthesized by the nuclear fusion that takes place with the bombardment of ²⁴²₉₄Pu by accelerated ²²₁₀Ne ions in the cyclotron at the Joint Institute for Nuclear Research at Dubna. The name of the element was proposed by Academician G. N. Flerov in honor of I. V. Kurchatov.

Kurchatovium is the first transactinide element. The electron configuration of Ku atoms in the gaseous phase is 5f¹⁴6d²7s², analogous to the configuration of the first translanthanide element hafnium (Hf: 4f¹⁴5d²6s²). This assumption is supported by the analogous chemical properties of the two elements. Thus, the anhydrous chloride of kurchatovium is similar in volatility to hafnium tetrachloride (sublimation temperature, 313°C) and much more volatile than the chlorides of the actinide elements (boiling point, greater than 1500°C). Using this property, the Czechoslovakian scientist I. Zvara and his co-workers carried out the chemical separation of Ku atoms from accompanying radioactive actinides in Dubna in 1966.

Thus, it was confirmed that kurchatovium belongs to a side subgroup of Group IV of the periodic table. American investigators later came to the same conclusion on the basis of a comparison of the chemical behavior of Ku, Hf, and actinides in aqueous solutions.

All of these studies have been carried out with a few dozen kurchatovium atoms, since the yield of the nuclear synthesis reaction is very low and the work is complicated by the extremely short lifetimes of Ku isotopes.

In 1969, American investigators proposed that element 104 be named Rutherfordium (symbol, Rf).

REFERENCE

Flerov, G.N., V. A. Druin, and A. A. Pleve. “Ustoichivost’ tiazhelykh iader i granitsa periodicheskoi sistemy elementov.” Uspekhi fizicheskikh nauk, 1970, vol. 100, issue 1.

G. N. FLEROV