Its properties, however, appear to be similar to those of Cs and the other alkali metals. Hydrogen gas is given off, which propels the the lithium metal across the water as it reacts. If the excess water is evaporated, the compound lithium hydroxide LiOH remains behind.
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Thus the equation for this reaction is. The elements sodium, potassium, rubidium, and cesium also combine violently with water to form hydroxides. The equations for their reactions are. Since the alkali metals all react with water in the same way, a general equation may be written:. In addition to their behavior when added to water, the alkali metals react directly with many elements.
All combine swiftly with oxygen in air to form white oxide:. Li 2 O is lithium oxide, Na 2 O is sodium oxide, etc. All except lithium react further to form yellow peroxides, M 2 O 2 :. Potassium, rubidium, and cesium are sufficiently reactive that yellow superoxides whose general formula is MO 2 can be formed:. Unless the surface of a sample of an alkali metal is scraped clean, it will appear white or gray instead of having a silvery metallic luster. This is due to the oxide, peroxide, or superoxide coating that forms after a few seconds of exposure to air. The following movie shows how a freshly cut piece of lithium is shiny, but dulls to gray when exposed to oxygen in the air.
The video also focuses on another important property of alkali metals: they are soft, and easy to cut, compared to other metals. A dull gray oxidized cylinder of lithium metal is cut, revealing a shiny silvery surface.
The Radioactivity of Potassium, Rubidium and Other Elements.
After 1 minute, the surface has dulled, and after 10 minutes, the cut surface has returned to the dull gray of the rest of the lithium metal. Since the alkali metal is lithium, the only reaction with oxygen that occurs is:. The alkali also combine directly with hydrogen gas to form compounds known as hydrides, MH:. These oxides, hydrides, hydroxides, and sulfides all dissolve in water to give basic solutions, and these compounds are among the strong bases. The peroxides and superoxides formed when the heavier alkali metals react with O 2 also dissolve to give basic solutions:.
By carefully washing this precipitate with boiling water they removed the more soluble potassium component and then confirmed that they really had a new element by examining the atomic spectrum of what remained. This showed two intense ruby red lines never seen before, indicating a new element, which they named after this colour. Atomic data. Glossary Common oxidation states The oxidation state of an atom is a measure of the degree of oxidation of an atom.
Oxidation states and isotopes. Glossary Data for this section been provided by the British Geological Survey. Relative supply risk An integrated supply risk index from 1 very low risk to 10 very high risk. Recycling rate The percentage of a commodity which is recycled. Substitutability The availability of suitable substitutes for a given commodity. Reserve distribution The percentage of the world reserves located in the country with the largest reserves.
Political stability of top producer A percentile rank for the political stability of the top producing country, derived from World Bank governance indicators. Political stability of top reserve holder A percentile rank for the political stability of the country with the largest reserves, derived from World Bank governance indicators.
Supply risk. Young's modulus A measure of the stiffness of a substance. Shear modulus A measure of how difficult it is to deform a material. Bulk modulus A measure of how difficult it is to compress a substance. Vapour pressure A measure of the propensity of a substance to evaporate. Pressure and temperature data — advanced. Listen to Rubidium Podcast Transcript :. You're listening to Chemistry in its element brought to you by Chemistry World , the magazine of the Royal Society of Chemistry. This week, we've got a radio active element that's good at keeping time but also has some fire in its belly.
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With more on the chemistry of rubidium, here's Tom Bond. In a way, the story of rubidium starts in when the German chemists Robert Bunsen and Gustav Kirchoff invented the spectroscope and in turn opened the door to a new age of chemical analysis. Before that the Bunsen burner had been developed to investigate the coloured flames they saw when combusting various metals and salts.
Bunsen and Kirchoff were able to work out that, by using an external light source and a prism, they could separate the wavelengths of emission spectra in these flames, and so the spectroscope was born. Caesium was their first major discovery using the spectroscope, followed quickly in by rubidium, which was detected by the red flame produced when they burnt the mineral lepidolite, which contains small amounts of rubidium. Bunsen and Kirchoff realised this colour came from an unknown substance and were then able to purify a small amount of rubidium.
Its name is derived from the Latin rubidus , meaning deepest red, which relates to the colour seen after excitation of the single electron in its outer shell.
Rubidium is actually one of our commoner elements and depending on which information source you look at, it is about the 16 th most abundant element in the earth's crust, with a concentration somewhere around 90 parts per million. Although it is relatively abundant compared with other elements such as copper, it is not found in a pure state but as a minor fraction in various minerals.
Most rubidium is derived as a by product of lepidolite extraction which has the primary goal of producing lithium. Rubidium is one of the alkaline metals, as group one of the periodic table are otherwise known.
As you move down Group 1 of the periodic table the reactivity of the elements increases which is in line with the increasing energy of the outer electron. While lithium and sodium added to water form part of school chemistry experiments, the extra reactivity of rubidium means the equivalent reaction requires caution and is not for the faint hearted. When a small amount of rubidium is chucked into water, the effect is pretty impressive, and in fact is so violent that the liberated hydrogen can ignite. Rubidium is so reactive that it can catch fire spontaneously in air, meaning it has to be stored under inert conditions.
In terms of their physical properties, the elements of Group 1 are soft metals with low-melting points.
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The element has two naturally occurring isotopes. Rubidium is the dominant form, accounting for 72 per cent of the total, while most of the remainder is the radioactive rubidium, which has a half-life of 50 billion years. The radioactive isotope decays to form strontium This process gives a way to age rocks, by measuring the isotopes of rubidium and strontium with mass spectrometry, then calculating the ratios of the radioactive forms to their decay products. Although it is chemically interesting, the element has relatively few commercial applications at present, but the amount of research activity suggests many possibilities exist.
One current use is in atomic clocks, though rubidium is considered less accurate than caesium. The rubidium version of the atomic clock employs the transition between two hyperfine energy states of the rubidium isotope. These clocks use microwave radiation which is tuned until it matches the hyperfine transition, at which point the interval between wave crests of the radiation can be used to calibrate time itself.
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Rubidium was chosen to investigate the unusual properties of extremely low-temperature fluids, known as Bose-Einstein condensates which have zero viscosity and the ability to spontaneously flow out of their containers. Their existence was predicted in by Einstein himself, who extended the work of Indian physicist S. Bose to suggest bosonic atoms at temperatures close to absolute zero would form their lowest possible energy state, which might allow quantum behaviour to be studied.
By the way, bosons are defined as atoms with integer spin, while multiple bosons can occupy the same energy state. It was not until the end of the 20 th century that technology advances made cooling elements close to absolute zero feasible. The first pure Bose-Einstein condensate was created using rubidium by a group from the University of Colorado in the US, and for this achievement they earned the Nobel Prize for physics. Rubidium is not particularly harmful to humans, and once in the body its ions are rapidly excreted in sweat and urine. Rubidium chloride has been used to study the transport of potassium ions in humans, since rubidium ions are not naturally found in the body and when present they are treated as if they were potassium.
In a similar way, because it tends to collect inside cells, especially tumours, the radioactive isotope Rb can be used to locate brain tumours. The low toxicity of rubidium is confirmed by a study from which aimed to assess the feasibility of using rubidium chloride as an anti-depressant, since similar effects had been observed in monkeys. After being given 23 grams of rubidium over 75 days, a volunteer showed no harmful side effects.
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It does though make you wonder whether equivalent clinical studies could take place now. Meanwhile, clinical applications of rubidium in psychiatry have yet to come to fruition. So there we have rubidium, the explosive red element number 37 in the periodic table. So this explosive element may have minimal commercial applications but can be used in atomic clocks and has isotopes that can locate brain tumours.