Rubidium is a chemical element in the periodic table that has the symbol Rb and atomic number 37. Rb is a soft, silvery-white metallic element of the alkali metal group. Rb-87, a naturally occurring isotope, is (slightly) radioactive. Rubidium is very soft and highly reactive, with properties similar to other elements in group 1, like rapid oxidation in air.
Notable characteristics
Rubidium is the second most electropositive of the stable alkaline elements and liquifies at high ambient temperature (102.7 F = 39.3 C). Like other group 1 elements this metal reacts violently in water. In common with potassium and caesium this reaction is usually vigorous enough to ignite the liberated hydrogen. Rubidium has also been reported to ignite spontaneously in air. Also like other alkali metals, it forms amalgams with mercury and it can form alloys with gold, caesium, sodium, and potassium. The element gives a reddish-violet color to a flame, hence its name.
Potential or current uses of Rubidium include:
A working fluid in vapor turbines.
A getter in vacuum tubes.
A photocell component.
The resonant element in atomic clocks. This is due to the hyperfine structure of Rubidium's energy levels.
An ingredient in special types of glass.
The production of superoxide by burning in oxygen.
The study of potassium ion channels in biology.
Rubidium is easily ionized, so it has been considered for use in ion engines for space vehicles (but caesium and xenon are more efficient for this purpose).
Rubidium compounds are sometimes used in fireworks to give them a purple color.
RbAg4I5 has the highest room temperature conductivity of any known ionic crystal. This property could be useful in thin film batteries and in other applications.
It has also been considered for use in a thermoelectric generator using the magnetohydrodynamic principle, where rubidium ions are formed by heat at high temperature and passed through a magnetic field. These conduct electricity and act like an armature of a generator thereby generating an electric current.
Rubidium, particularly 87Rb, in the form of vapor is one of the most commonly-used atomic species employed for laser cooling and Bose-Einstein condensation. Its desirable features for this application include the ready availability of inexpensive diode laser light at the relevant wavelength and the moderate temperatures required to obtain substantial vapor pressures.
Also, Rubidium is used for polarizing 3He. Polarized Rb polarizes 3He by hyperfine interaction. Polarized 3He cells are becoming popular for polarizing neutrons and also for neutron polarization measurements.
Electrical conductivity 7.79 106/(m·ohm)
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