Rubidium
Rubidium is a chemical element on the periodic table whose symbol is Rb and its atomic number is 37.
Rubidium is a very soft, silvery-white metal from the group of alkali metals. The metallic rubidium shares similarities with potassium and cesium in terms of its physical appearance, softness, and conductivity. Rubidium cannot be stored under atmospheric oxygen, as a highly exothermic reaction would occur, sometimes even igniting the rubidium. metal.
Rubidium is the first alkali metal in the group to have a density greater than that of water, so | it sinks, unlike the metals above it in the group. Rubidium has an atomic weight of 85.4678. On Earth, naturally occurring rubidium consists of two isotopes: 72% is a stable isotope 85Rb and 28% is a slightly radioactive isotope 87Rb, with a lifetime average of 48.8 billion years, more than triple the estimated age of the universe.
German chemists Robert Bunsen and Gustav Kirchhoff discovered rubidium in 1861 using the newly developed technique, flame spectroscopy. The name comes from the Latin word rubidus, meaning deep red, the color of its emission spectrum. Rubidium compounds have various chemical and electronic applications. Metallic rubidium is easily vaporized and has a convenient spectral absorption range, making it a frequent target for manipulation of atom lasers. Rubidium is not a known nutrient for any living organisms. However, rubidium ions have similar properties and the same charge as potassium ions, and are taken up and actively processed by animal cells in a similar way.
Main features
Rubidium is a soft, bright silvery-white alkali metal that tarnishes rapidly in air, highly reactive. Like the other elements of group 1, it can burn spontaneously in air with a yellowish-violet flame, it reacts violently with water, giving off hydrogen, and forms an amalgam with mercury. It can form alloys with gold, the other alkali and alkaline earth metals, antimony and bismuth.
Rubidium is a very soft, ductile, silvery-white metal. It is the second most electropositive of the stable alkali metals, melting at a temperature of 102.7 °F (39.3 °C). Like other alkali metals, rubidium metal reacts violently with water. As with potassium (which is slightly less reactive) and cesium (which is slightly more reactive), this reaction is usually vigorous enough to ignite the hydrogen gas it produces. Rubidium has also been reported to ignite spontaneously in air. It forms amalgams with mercury and alloys with gold, iron, cesium, sodium, and potassium but not with lithium, although rubidium and lithium are in the same group.
Like other alkali metals, it has a single oxidation state (+1) and reacts with carbon dioxide, hydrogen, nitrogen, sulfur and halogens. Its production ranks 16th among the most abundant metals in the earth's crust.
Compounds
Rubidium chloride (RbCl) is probably the most widely used rubidium compound: among various other chlorides, it is used to induce living cells to take up DNA; it is also used as a biomarker, as it is found in nature only in small amounts in living organisms and, when present, replaces potassium. Other common rubidium compounds are the corrosive rubidium hydroxide (RbOH), the starting material for most rubidium-based chemical processes; rubidium carbonate (Rb2CO3), used in some optical glasses, and rubidium copper sulfate, Rb2SO< sub>4CuSO46H2O. Silver rubidium iodide (RbAg4I5) has the highest conductivity at room temperature of any known ionic crystal, a property exploited in thin-film batteries and others Applications.
Presence
Rubidium is the 23rd most abundant element in the Earth's crust, roughly as abundant as zinc and considerably more common than copper. It occurs naturally in the minerals leucite, polucitecarnalite, and zinnwaldite that contain up to 1% oxide rubidium. Lepidolite contains between 0.3% and 3.5% rubidium and is the commercial source of the element. Some potassium ores and potassium chlorides also contain the element in commercially significant amounts.
Seawater contains an average of 125 µg/L rubidium compared to the much higher value for potassium of 408 mg/L and the much lower value of 0.3 µg/L for cesium. rubidium is the eighteenth most abundant element in seawater.
Due to its large ionic radius, rubidium is one of the " incompatible elements ". During magma crystallization, rubidium is concentrated together with its heavier analogue, cesium, in the liquid phase and crystallizes last. Therefore, the largest rubidium and cesium deposits are zonal pegmatite orebodies formed by this enrichment process. Because rubidium substitutes for potassium in magma crystallization, enrichment is much less effective than cesium. Zone pegmatite ore bodies that contain mineable amounts of cesium as pollucite or the lithium minerals lepidolite are also a source of rubidium as a by-product.
Two notable sources of rubidium are the rich pollucite deposits at Bernic Lake, Manitoba, Canada, and rubiclin ((Rb,K)AlSi 3O8)) found as impurities in pollucite on the Italian island of Elba with a rubidium content of 17.5%. Both deposits are also sources of cesium.[citation needed]
Applications
Rubidium can be easily ionized, so its use in ion engines for spacecraft has been studied, although xenon and cesium have been shown to be more effective for this purpose. It is mainly used in the manufacture of special glass for fiber optic telecommunication systems and night vision equipment. Other uses are:
- Photo-emitter coatings of telurio-rubidium in photoelectric cells and electronic detectors.
- Vacuum tuner, getter, (substance that absorbs the latest gas traces, especially oxygen) in vacuum tubes to ensure its proper operation.
- Photo resistance component (or LDR, Light dependant resistors, resistances dependent on light), resistances in which electrical resistance varies with the lighting received.
- In medicine for postitron emission tomography, treatment of epilepsy and ultracentrifugal separation of nucleic acid and virus.
- Workflow in steam turbines.
- The RbAg4I5 has the greatest electrical conductivity known at room temperature of all ionic crystals and could be used in the manufacture of batteries in the form of thin sheets among other electrical applications.
- The possibility of using the metal in thermoelectric generators based on magnetohydrodynamics is studied so that the rubid ions generated at high temperature are driven through a magnetic field generating an electric current.
- Serve to get the purple in the fireworks.
In many applications it can be substituted for cesium (or the corresponding cesium compound) because of its chemical similarity.
History
Rubidium (from the Latin rubidus, dark red) was discovered in 1861 by Robert Bunsen and Gustav Kirchhoff in lepidolite using a spectroscope to detect the two red lines characteristic of the emission spectrum of this element and which are the reason for its your name. There are few industrial applications of this element, which in 1920 began to be used in photoelectric cells, having been used mainly in research and development activities, especially in chemical and electronic applications.
Abundance and obtaining
Although rubidium is more abundant in the earth's crust than cesium, limited applications and the lack of a rubidium-rich mineral limits the production of rubidium compounds to 2-4 tons per year.
Rubidium is very abundant in the earth's crust, since it is among the 56 elements that together comprise 0.05% of its weight, it cannot be considered scarce. Representing the order of 78 ppm by weight, it is the 23.er element and the 16th most abundant.º of metals surpassing other common metals such as copper, lead and zinc from which thousands of tons are extracted per year compared to three for rubidium. It is also 30 times more abundant than cesium and 4 times than lithium, the metals from which it is extracted as a by-product. The reason for this disparity is that there are no known minerals in which rubidium is the predominant element and that its ionic radius is very similar to that of potassium (2000 times more abundant), replacing it —in minute quantities— in its mineral species where it appears as impurity.
It is found in various minerals such as leucite, pollucite and zinnwaldite. Lepidolite contains 1.5% rubidium (it can sometimes exceed 3.15%) and is where most of the metal is obtained; also other potassium ores and potassium chloride contain significant amounts of rubidium to allow their profitable extraction, as well as the pollucite deposits (which can contain up to 1.35% rubidium) among which those of Bernic Lake in Manitoba stand out., (Canada).
The metal is obtained, among other methods, by reducing rubidium chloride with calcium in a vacuum, or by heating its hydroxide with magnesium in a stream of hydrogen. Small quantities can be obtained by heating their compounds with chlorine mixed with barium oxide in a vacuum. The purity of the marketed metal varies between 99 and 99.8%.
Isotopes
24 rubidium isotopes are known and only two exist in nature, Rb-85 and the radioactive Rb-87. Normal rubidium mixtures are slightly radioactive.
The isotope Rb-87, which has a half-life of 48.8 × 10 9 years, has been widely used for radiometric dating of rocks. Rb-87 decays to stable Sr-87 emitting a negative beta particle. During fractional crystallization, the strontium tends to concentrate in the plagioclase, leaving the rubidium in the liquid phase, so that the Rb/Sr ratio in the residual magma increases over time. The largest ratios—of 10 or more—are found in pegmatites. If the initial amount of strontium is known or can be extrapolated, measuring the concentrations of Rb and Sr and the ratio Sr-87/Sr-86 can determine the age of the rock. Obviously, the measured age will be that of the rock if it has not undergone alterations after its formation.
The resonance frequency of the Rb-87 atom is used as a reference in standards and oscillators used in radio and television transmitters, in telecommunication network synchronization, and in navigation and satellite communication. The isotope is also used in the construction of atomic clocks.
The Rb-82 isotope is used in positron emission tomography imaging of the heart. Due to its short half-life (1,273 minutes) it is synthesized, before its administration, from strontium-82 since in just one day it almost completely disintegrates
Precautions
Rubidium reacts violently with water, causing the hydrogen released in the reaction to ignite:
- 2 Rb + 2 H2O → 2 RbOH + H2
To ensure the purity of the metal and safety in its handling, it is stored under dry mineral oil, under vacuum or in an inert atmosphere.
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