californium

Japanese: カリホルニウム

Cf. Atomic number 98. Group 3 actinide element with electronic configuration [Rn]5f ¹⁰ 7s ^2. Sixth transuranium element discovered. Named after the University of California, California, where experiments were carried out. 244 Cf was obtained in 1950 by G. T. Seaborg, A. Ghiorso and others by bombardment of ²⁴² Cm with ³⁵ MeV ⁴ He nuclei (alpha particles) accelerated in a 60 in cyclotron at the University of California, Berkeley. Obtained by sequential neutron absorption (in a nuclear reactor). ^249,252 Cf is used. Metal with density 15.1 g cm ^-3 and melting point 1173 °C. First ionization energy 608 kJ mol ^-1 (6.3 eV). Usual oxidation states 2-4. CfO, Cf ₂ O ₃ , CfO ₂ , and CfCl ₃ were produced. Currently, 20 isotope nuclides are known, ranging from 237 to 256. The nuclide with mass number 251 is the longest-lived, with a half-life of 898 y. The half-life of ²⁵⁴ Cf was initially thought to be 55 d, which coincided with the half-life of the luminosity decay of a supernova, and it was thought to have been synthesized in space, but this was later revised to 60.5 d, and this theory is considered to be insufficiently supported. ²⁵² Cf, which has a half-life of 2.645 y, undergoes alpha decay (97%) and spontaneous fission (3%), and since it produces neutrons during spontaneous fission, it is used as a portable neutron source for on-site gold and silver exploration by activation analysis. [CAS 7440-71-3]

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

Japanese:

Cf．原子番号98の元素．電子配置[Rn]5f¹⁰7s²の周期表3族アクチノイド元素．6番目に発見された超ウラン元素．実験の行われたカリフォルニア大学，カリフォルニア州にちなんで命名された．1950年，G.T. Seaborg(シーボーグ)，A. Ghiorsoらにより，カリフォルニア大学(バークレー校)の60 inサイクロトロンで加速した35 MeV⁴He原子核(α粒子)による ²⁴²Cm の衝撃で ²⁴⁴Cf が得られた．逐次中性子吸収(原子炉中)で得られる．^249,252Cf が利用される．密度15.1 g cm^－3，融点1173 ℃ の金属．第一イオン化エネルギー608 kJ mol^－1(6.3 eV)．通常の酸化数2～4．CfO，Cf₂O₃，CfO₂，CfCl₃がつくられた．現在，知られている同位体核種は，237～256の範囲に20種．質量数251の核種がもっとも長寿命で半減期898 y．²⁵⁴Cf の半減期は当初55 d とされ，超新星の光度減衰の半減期と一致するとして宇宙での合成が考えられたが，その後60.5 d と訂正されたのでこの説は根拠が不十分と考えられている．半減期2.645 y でα崩壊(97％)および自発核分裂(3％)する ²⁵²Cf は，自発核分裂の際に中性子を発生するので，ポータブル中性子源として放射化分析による現場での金，銀探索に使われる．[CAS 7440-71-3]