lawrencium 化学特性,用途語,生産方法
発見
周期表元素記号＝Lr 原子番号＝103電子配置＝［Rn］5f146d17s2 おもな酸化数＝III周期表第IIIA族に属する希土類元素のうちのアクチノイドの一つ。1961年5月カリフォルニア大学のローレンス研究室で，アメリカのギオーソA.Ghiorsoらが，カリホルニウム(249Cf,250Cf,251Cf,252Cfの混合物)に線形加速器で加速したホウ素(10Bまたは11B)のイオンを衝撃して，核反応生成物中に半減期8±2秒のα放出体を発見し，103番元素であることを確かめた。
1961年カリフォルニア大学ローレンス放射線研究所において、重イオン線形加速器で加速したホウ素イオンでカリホルニウムを衝撃して、質量数257（のちに258に訂正された）の103番元素を合成したとするのが最初の報告で、1965年にはソ連の研究グループがアメリシウムの酸素イオン衝撃で質量数256の同位体を合成した。10種を超える同位体が得られているが、いずれも半減期は短い。そのため化学的性質を調べるのは困難であるが、溶液中で酸化数＋Ⅲとなる証拠が得られている。サイクロトロンの発明者であるアメリカのローレンスを記念して命名された。発見当初、元素記号としてLwが使われたこともあったが、1997年に、国際純正・応用化学連合（IUPAC：International Union of Pure and Applied Chemistry）によって、Lrが正式に決定された。
解説
Lr．原子番号103の元素．電子配置[Rn]5f 146d17s2の周期表3族アクチノイド元素．サイクロトロンを発明したE.O. Lawrenceにちなんで命名された．1961年3月，カリフォルニア大学(バークレー校)のA. Ghiorsoらは，249,250,251,252Cf の混合物3 mg を重イオン線形加速器(HILAC)で加速した 10B または 11B イオンで衝撃し，半減期8 s でα崩壊する質量数257の核種を合成したと発表した．1965～1967年，ソビエト(当時)・ドゥブナの原子核合同研究所(JINR)のG.N. Flerov(フレロフ)らは，この核種を確認できないと報告した．1970年，バークレーグループは質量数256の核種のわずか10原子を使って溶媒抽出実験を行い，Lrは直前の No2＋ より，原子番号の若いアクチノイド元素の三価イオンに似たふるまいをすると結論した．酸化数2，3．現在，知られている同位体核種は，252～266の範囲に15種．最新のデータでは，質量数256のα崩壊核種は半減期27 s．261Lr 39 min，262Lr 4 h(ともに自発核分裂)．森北出版「化学辞典（第2版）
物理的性質
The nuclear chemists at the Lawrence Berkeley Laboratory worked with extremely smallsamples of lawrencium with short half-lives, which made it difficult to determine the newelement’s chemical and physical properties. Most of its isotopes spontaneously fission as theygive off alpha particles (helium nuclei). Lawrencium’s melting point is about 1,627°C, but itsboiling point and density are unknown.
同位体
There are a total of 14 isotopes of lawrencium. Lawrencium-252 has the shortesthalf-life of just 0.36 of a second, and lawrencium-262 has the longest half-life of fourhours. None are found in nature. All the isotopes of lawrencium are artificially manufacturedin particle accelerators or nuclear reactors.
名前の由来
Named for and in honor of Ernest O. Lawrence, who invented the
cyclotron.
天然物の起源
Because lawrencium does not exist in nature, it had to be produced artificially. This wasdone in 1961 by the team of scientists at Berkeley, using an ion accelerator to bombard threedifferent isotopes of the element californium with heavy ions of the elements
10boron and
11boron along with some neutrons that produced the isotope
103Lr-258. The resulting productweighed only about two millionths of a gram and had a half-life of only 4.1 seconds, fissioningspontaneously.
特性
Lawrencium is the last of the transuranic elements and the 15th in the actinide series (thereare 15 elements in the lanthanide series as well, assuming you start counting the series at theelements lanthanide and actinium, respectively.) It is assumed that lawrencium has somechemical and physical characteristics similar to lutetium, located just above it in the lanthanideseries. It is also located at the bottom of the group 17 (VIIA) elements, which makes itthe heaviest of the halides.
来歴
Lawrencium as the 5f transition elements (actinide series) was discovered in March 1961 by A. Ghiorso, T. Sikkeland, A. E. Larsh, and R. M. Latimer. A 3-μg californium target, consisting of a mixture of isotopes of mass number 249, 250, 251, and 252, was bombarded with either
10B or
11B. The electrically charged transmutation nuclei recoiled with an atmosphere of helium and were collected on a thin copper conveyor tape which was then moved to place collected atoms in front of a series of solid-state detectors. The isotope of element 103 produced in this way decayed by emitting an 8.6-MeV alpha particle with a half-life of 8 s. In 1967, Flerov and associates of the Dubna Laboratory reported their inability to detect an alpha emitter with a half-life of 8 s which was assigned by the Berkeley group to 257103. This assignment has been changed to
258Lr or
259Lr. In 1965, the Dubna workers found a longer-lived lawrencium isotope,
256Lr, with a half-life of 35 s. In 1968, Ghiorso and associates at Berkeley were able to use a few atoms of this isotope to study the oxidation behavior of lawrencium. Using solvent extraction techniques and working very rapidly, they extracted lawrencium ions from a buffered aqueous solution into an organic solvent, completing each extraction in about 30 s. It was found that lawrencium behaves differently from dipositive nobelium and more like the tripositive elements earlier in the actinide series. Ten isotopes of lawrencium are now recognized.
使用
There are no common uses. So little of it exists that it has no use outside of basic scientificresearch.
定義
lawrencium: Symbol Lr. A radio radioactivemetallic transuranic element belonging to the actinoids; a.n. 103;mass number of the first discoveredisotope 257 (half-life 8 seconds). Anumber of very short-lived isotopes have now been synthesized. The elementwas identified by AlbertGhiorso and associates in 1961. It was named after E. O. Lawrence(1901–58).
危険性
Like the other short-lived radioactive isotopes, lawrencium is a radiation hazard. Also, aswith the others, the danger to individuals and the public is small since there is not much of itin existence. Also, the small amount that has been produced has a short half-life, so over shortperiods of time it ceases to exist.
lawrencium 上流と下流の製品情報
原材料
準備製品