Рубидий

Химические свойства

Rubidiumis a soft, silvery white metallic element. It is solid at room temperature, but melts easily at 39.3°C. Similar to the other group 1metals, rubidium reacts exothermically in water, forming corrosive rubidium hydroxide (RbOH) and hydrogen gas, Easily oxidized in air.High heat capacity and heat transfer coefficient. Soluble in acids and alcohol.

Физические свойства

Rubidium is a silvery-white lightweight solid at room temperature, but it melts at just 38.89°C (102°F), which is just over the human body's normal temperature. It's boiling point is 686°C, it's density is 1.532 g/cm3, and it has an oxidation state of +1.

Изотопы

There are 30 isotopes of rubidium, ranging from Rb-75 to Rb-98. Rb-85 is theonly stable form of rubidium and constitutes 72.17% of all rubidium isotopes found inthe Earth’s crust. Rb-87 is radioactive (a half-life of 4.9×1010 years) and makes up about27.83% of the remainder of rubidium found in the Earth’s crust. All the other 28 isotopes make up a tiny fraction of all the rubidium found on Earth and are radioactive withvery short half-lives.

Происхождение имени

Rubidium is named for the Latin word rubidus, meaning “reddish.

Вхождение

Rubidium does not exist in its elemental metallic form in nature. However, in compoundforms it is the 22nd most abundant element on Earth and, widespread over most land areasin mineral forms, is found in 310 ppm. Seawater contains only about 0.2 ppm of rubidium,which is a similar concentration to lithium. Rubidium is found in complex minerals and untilrecently was thought to be a rare metal. Rubidium is usually found combined with other Earthmetals in several ores. The lepidolite (an ore of potassium-lithium-aluminum, with traces ofrubidium) is treated with hydrochloric acid (HCl) at a high temperature, resulting in lithiumchloride that is removed, leaving a residue containing about 25% rubidium. Another processuses thermochemical reductions of lithium and cesium ores that contain small amounts ofrubidium chloride and then separate the metals by fractional distillation.

Характеристики

Rubidium is located between potassium and cesium in the first group in the periodic table.It is the second most electropositive alkali element and reacts vigorously and explosively in airor water. If placed on concrete on a sunny day, it would melt and then react violently withmoist air to release hydrogen with enough heat to burn the hydrogen. If a chunk of rubidiummetal is left on a table exposed to the air, it combusts spontaneously. Rubidium must be storedin oil, such as kerosene.

Использование

Because rubidium is a much larger atom than lithium or sodium, it gives up its outer valence electron easily, thus becoming a positive ion (oxidation state = Ru+). Rubidium forms numerous compounds, but only a few are useful. One of the main uses for rubidium is as a getter in vacuum tubes used in early radios, TVs, and cathode-ray tubes. When rubidium gas is placed in sealed glass cells along with an inert gas, it becomes a rubidium-gas cell clock. Because of the consistent and exact frequency (vibrations) of it atoms, it is a very accurate timekeeper. Rubidium and selenium are used in the manufacture of photoelectric cells, sometimes called electric eyes. Rubidium is a very caustic alkali (base) with a high pH value that makes it an excellent reducing agent (highly electropositive) in industry and chemical laboratories. A unique use is its ability to locate brain tumors. It is a weak radioisotope able to attach itself to diseased tissue rather than healthy tissue, thus making detection possible.

Определение

rubidium: Symbol Rb. A soft silvery white metallic element belonging togroup 1 (formerly IA) of the periodictable; a.n. 37; r.a.m. 85.47; r.d. 1.53;m.p. 38.89°C; b.p. 688°C. It is foundin a number of minerals (e.g. lepidolite)and in certain brines. The metalis obtained by electrolysis of moltenrubidium chloride. The naturally occurringisotope rubidium–87 is radioactive(see rubidium–strontiumdating). The metal is highly reactive,with properties similar to those ofother group 1 elements, ignitingspontaneously in air. It was discoveredspectroscopically by Robert Bunsenand Gustav Kirchhoff in 1861.

Подготовка

Although rubidium metals have been prepared by fused salt electrolysis, the highly reactive nature of the metals complicates the collection step and favors the use of other preparative methods where the metals can be removed in vapor form from the reaction mixture. The oxides, hydroxides, carbonates, halides, sulphates, chromates and nitrates of rubidium have been reduced to the metals by strong reducing metals such as sodium, calcium, magnesium, barium, iron, zirconium, aluminum or silicon at moderately high temperatures. The preferred method, however, involves the reduction of the anhydrous metal chlorides with calcium metal under vacuum. Anhydrous rubidium chloride is mixed with a large excess of calcium chips and heated under vacuum at 700- 800°C. As the chloride is reduced, metal vapors issue from the reaction mixture and are led under the vacuum to a cooler portion of the vessel where they condense and drop into a collection vessel.

Общее описание

A soft silvery metal. Shipped in very limited quantities sealed in a copper tube and over packed in a wooden box. Used in electronics.

Реакции воздуха и воды

Tarnishes rapidly upon exposure to air. Reacts violently with water to form corrosive RUBIDIUM hydroxide and hydrogen, a flammable gas. The heat of the reaction usually ignites the hydrogen.

Профиль реактивности

RUBIDIUM METAL is a strong reducing agent. Burns spontaneously in dry oxygen [Mellor 2:468 1946-47]. Readily catches fire in air when molten or with a sulfur vapor [Mellor 2: 469 1946-47]. Causes explosive decomposition of maleic anhydride. [Chem Safety Data Sheet SD-88 1962; Chem. Haz. Info. Series C-71 1960] Burns in chlorine [Mellor 2, Supp. 1:380 1956]. Interaction with mercury is exothermic and may be violent, [Mellor, 1941, Vol. 2, 469].

Опасность

The major hazard is from fire and explosions of the elemental metallic form of rubidium.It must be stored in an inert atmosphere or in kerosene. When rubidium contacts skin, itignites and keeps burning and produces a deep, serious wound. Water and blood just make itreact more vigorously.
Many of the compounds of rubidium are toxic and strong irritants to the skin and lungs.It is one of the elements best left to experienced handlers.
Very small traces of rubidium are found in the leaves of tobacco, tea, and coffee, as well asin several edible plants, but these radiation traces are harmless when used in moderation.

Угроза здоровью

Inhalation or contact with vapors, substance or decomposition products may cause severe injury or death. May produce corrosive solutions on contact with water. Fire will produce irritating, corrosive and/or toxic gases. Runoff from fire control may cause pollution.

Пожароопасность

Produce flammable gases on contact with water. May ignite on contact with water or moist air. Some react vigorously or explosively on contact with water. May be ignited by heat, sparks or flames. May re-ignite after fire is extinguished. Some are transported in highly flammable liquids. Runoff may create fire or explosion hazard.

Профиль безопасности

Moderately toxic by intraperitoneal route. A very reactive alkali metal (more reactive than potassium or cesium). In the body, rubidlum substitutes for potassium as an intracellular ion. The ratio of Rb/K intake is important in the toxicology of rubidium. A ratio above 40% is dangerous. In rats, a failure to gain weight is the first symptom, followed by ataxia and hyperirritabhty. Symptoms include: skin ulcers, poor hair coat, sensitivity, and extreme nervousness leading to convulsions and death. hazard when exposed to heat or flame or by chemical reaction with oxidlzers. Igmtes on contact with air, oxygen, and halogens. A very dangerous fire and explosion RUBIDIUM HYDROXIDE RPZOOO 121 5 Ignites spontaneously on contact with water. Reaction with water, moisture, or steam forms explosive hydrogen gas, whch then ignites. Explodes in contact with liquid bromine. Can react explosively with air, halogens, mercury, nonmetals, vanadium chloride oxide, moisture, acids, oxidizers. Violent reaction with vanadium trichloride oxide (at 60℃C), Cl202, P. Molten rubidium ignites in sulfur vapor and reacts vigorously with carbon. RbOH is more basic than KOH. Storage and handling: Keep under benzene, petroleum, or other liquids not containing gaseous O2. When heated to decomposition it emits toxic fumes of RbzO. See also SODIUM and SODIUM POTASSIUM ALLOY.