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Rubidium
Rubidium is a relatively common element with an estimated concentration of about 90 parts per million, ranking about 16th in the Earth's crust in abundance. It is found as a minor component in many different minerals and not in its pure form, although it is more prevalent than elements like copper. The main objective of lepidolite extraction is to produce lithium, with most rubidium being a byproduct of this process. Typically, pure rubidium is obtained by reducing rubidium chloride using metallic calcium at low pressure and around 750°C.
1.0Introduction
With an atomic number of 37 and an average atomic mass of 85.47 g/mol, rubidium (Rb) is a member of the alkali metal group. Found by Kirchhoff and Bunsen in 1860, natural rubidium is a mixture of two isotopes: radioactive Rubidium-87 (27.85%) and Rubidium-85 (72.15%), making up around 0.01% of the Earth's crust.
Rubidium is a silvery-white, extremely soft metal and one of the most reactive elements on the periodic table. Its density is approximately 1.5 times that of water. Rubidium is solid at room temperature, though it melts with only a slight increase in temperature.
2.0Physical Properties of Rubidium
3.0Chemical Properties of Rubidium
- Reactivity: Highly reactive, rubidium must be stored in dry mineral oil to prevent spontaneous ignition when exposed to air. It reacts vigorously with water, forming rubidium hydroxide (RbOH) and hydrogen gas, which ignites spontaneously:
2Rb+2H2O→2RbOH+H2 - Oxides Formation: When exposed to air, rubidium forms various oxides such as rubidium monoxide (Rb2O), rubidium suboxides (Rb6O, Rb9O2), and, in the presence of excess oxygen, rubidium superoxide (RbO2).
- Reaction with Halogens: Rubidium readily reacts with halogens to produce rubidium halides, such as:
- Rubidium fluoride (RbF)
- Rubidium chloride (RbCl)
- Rubidium bromide (RbBr)
- Rubidium iodide (RbI).
4.0Uses of Rubidium
- Fireworks: Rubidium compounds produce a purple colour in fireworks displays.
- Thermoelectric Generators: In thermoelectric generators, rubidium operates using the magnetohydrodynamic principle, where hot rubidium ions move through a magnetic field to generate electricity.
- Laser Cooling and Bose-Einstein Condensation: Vaporized rubidium-87 (87Rb^{87}Rb87Rb) is one of the most commonly used elements for laser cooling and creating Bose-Einstein condensates.
- Cold-Atom Applications: Because of its broad Feshbach resonance spectrum, rubidium-85 (85Rb^{85}Rb85Rb) is the preferred material for applications needing adjustable interactions.
- Atomic Clocks: Rubidium is perfect for atomic clocks because of its hyperfine structure, which offers high-precision timing.
- Secondary frequency references, also known as rubidium oscillators, are mostly made of rubidium and are utilised in various electronic transmission, networking, and testing devices, including cell site transmitters.
- Vapour Turbines and Vacuum Tubes: Rubidium is a working fluid in vapour turbines, a getter in vacuum tubes, and a photocell component.
- Specialty Glass and Research: Rubidium is a crucial ingredient in certain types of glass. It is used to produce superoxide, study potassium ion channels in biological systems, and as a vapour in atomic magnetometers.
- Medical Imaging: Rubidium-82 is utilised in positron emission tomography (PET) scans for medical imaging.