Rubidium is a soft, silvery metal that belongs to the alkali metal group in the periodic table. It’s not as well known as sodium or potassium, but it has some really interesting properties. You’ll mostly find rubidium in minerals, and it’s so creative that it can even catch fire in air or water! Even though it’s not very common in everyday life, rubidium plays an important role in science and technology. Let’s scroll down to know all about it.

Rubidium

Rubidium is a chemical element with the atomic number 37 and the chemical symbol Ru. It is a member of the first group, (alkali metals) of the periodic table. It is one of the most alkaline and electropositive elements. In 1861, German chemists Robert Bunsen and Gustav Kirchhoff used the newly invented method of flame spectroscopy to discover rubidium from the mineral lepidolite.

Since rubidium has a melting point of roughly 40°C, it can only be liquid at room temperature on a hot day. At -100 oC, it interacts aggressively with water and even ice, igniting spontaneously in the air and exploding the released hydrogen. It combines with mercury to make amalgams, just like all the other alkali metals. It forms alloys with sodium, potassium, cesium, and gold. Its flame is violet-yellow in colour.

Rubidium is mono isotopic, however, it exists in two isotopes in the Earth’s crust: the radioactive \(^{87}Rb\) (which has a half-life of around \(6\times 10^{11}\) years) and the stable \(^{85}Rb (72.2%)\). From rubidium-74 to rubidium-102, many radioactive isotopes have been created artificially.

However, rubidium is more dispersed and rarely forms a natural mineral. It is only discovered as an impurity in other minerals, with concentrations of up to 5% in minerals like lepidolite, pollucite, and carnallite.

The atomic number of rubidium is 37 which also indicates the number of electrons and protons in an atom of rubidium. Therefore, the electron configuration of rubidium can be written as

\(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{6}5s^{1}\)

Valency of Rubidium

Properties of Rubidium

The physical and chemical properties of rubidium are discussed as follows:

Physical Properties of Rubidium

• It exists as a silvery-white metallic solid with a body-centered crystal structure.
• It has an atomic weight of 85.468 g/mol with a density of \(1.532 g/cm^3\).
• Its melting point is 312.45 K (39.30 °C, 102.74 °F).
• Its boiling point is 961 K (688 °C, 1270 °F).

Chemical Properties of Rubidium

• Rubidium must be stored in dry mineral oil. If exposed, it spontaneously catches fire in the air and reacts strongly with water to produce a solution of rubidium hydroxide (RbOH) and hydrogen which ignites spontaneously.
• Rubidium forms rubidium hydroxide and hydrogen on hydrolysis.

\(2Rb + 2H_{2}O \rightarrow 2RbOH + H_{2}\)

• When exposed to air, rubidium produces a variety of oxides, such as rubidium monoxide \(Rb_{2}O, Rb_{6}O, and \ Rb_{9}O_{2}\). Rubidium that has too much oxygen produces the superoxide \(RbO_{2}\).
• Rubidium creates the compounds rubidium fluoride, rubidium chloride, rubidium bromide, and rubidium iodide when combined with halogens.

Uses of Rubidium 

Rubidium is a highly reactive metal with a wide range of applications:

• It has been used to manufacture specific types of glass, to clean oxygen traces out of vacuum tubes, and as a part of photocells. Light energy is transformed into electrical energy by a photocell.
• It was explored for use in ion engines because it can be easily ionized, but cesium was found to be more efficient. Additionally, it has been suggested for use in thermoelectric generators and as a working fluid for vapour turbines.
• Fireworks occasionally contain rubidium nitrate to give them a purple hue.
• The primary coronary arteries get blocked during ischemia, which is also best monitored using rubidium.
• It has been used to find brain tumours since it is mildly radioactive and gathers in tumours but not in healthy tissue.

Effects of Rubidium

The high electropositive nature and reactivity of rubidium are responsible for the hazardous effects of rubidium on human health.

• When consumed, rubidium is moderately harmful. Thermal burns will result if rubidium catches on fire. Rubidium hydroxide, which causes chemical burns to the skin and eyes, is easily formed when rubidium combines with skin moisture.
• Burns to the skin and eyes are signs and symptoms of overexposure. Ataxia, hyperirritability, skin ulcers, failure to gain weight, and excessive anxiety are the most common practice problems arising due to rubidium exposure.

No specific environmental effects of rubidium have been observed to date.

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