Radium - radium (English spelling)

Japanese: ラジウム - らじうむ（英語表記）radium

It belongs to Group 2 of the periodic table and is one of the alkaline earth metals. It is a typical radioactive element.

history

Radium was discovered in uranium ore together with polonium by the French Curies in 1898. It was the first radioactive element, and the method of separation and confirmation at that time was also the first classical example of radiochemical analysis. The name radium comes from the Latin "radius," which means radiation. Radioactivity was first discovered with uranium, but the discovery of radium, which has a much stronger radioactivity than uranium, marked the beginning of full-scale research into radioactivity.

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Existence

There are four natural isotopes of radium: radium-223 (actinium X, AcX) in the actinium series, radium-224 (thorium X, ThX) in the thorium series, radium-226 in the uranium-radium series, and radium-228 (mesothorium 1, MsTh ₁ ) in the thorium series. Radium-226 was discovered by Marie Curie, and is often referred to simply as radium. This is the most important isotope, and is found in all uranium ores; for example, about 200 milligrams are present in one ton of pitchblende.

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Manufacturing method

It is found only in uranium ores; it is separated along with barium, converted to its chloride salt, and then separated from the barium by fractional crystallization or ion exchange resins.

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nature

A metal with a white luster. It resembles barium but is more volatile than barium. When exposed to air, its surface turns black. It reacts with water to become radium hydroxide and generate hydrogen. When it comes into contact with oxygen, it becomes an oxide. It generally exhibits properties similar to those of other alkaline earth metal elements, but is more violent. Its flame color reaction is red.

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Applications

Radium-226 has a half-life of 1,590 years and is used as an ideal standard for radioactivity. It has been used as a gamma ray source in medicine and industrial radiography, but other inexpensive artificial radioisotopes have recently come to be used.

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[References] | Radium Therapy [Supplementary Materials] | Radium (Data Notes)

Periodic Table
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Periodic Table

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

Japanese:

周期表第2族に属し、アルカリ土類金属元素の一つ。代表的な放射性元素である。

歴史

1898年にフランスのキュリー夫妻によってポロニウムとともにウラン鉱石から発見された。放射性元素として最初のものであり、そのときの分離確認の方法は、放射化学分析の最初の古典的実例でもある。ラジウムの名称は、放射線を意味するラテン語radiusにちなんだものである。放射能の発見はウランについて初めてなされたものであるが、ウランよりはるかに強い放射能をもつラジウムの発見は放射能に関する本格的研究の端緒となった。

［鳥居泰男］

存在

天然には、アクチニウム系列のラジウム223（アクチニウムX、AcX）、トリウム系列のラジウム224（トリウムX、ThX）、ウラン・ラジウム系列のラジウム226、トリウム系列のラジウム228（メソトリウム1、MsTh₁）の4種の同位体が存在する。キュリー夫妻によって発見されたものはラジウム226で、単にラジウムというときはこれをさすことが多い。これは同位体中もっとも重要なもので、すべてのウラン鉱石中に含まれており、たとえばピッチブレンド1トン中には約200ミリグラム存在する。

［鳥居泰男］