Rubidium is a silvery-white and extremely soft metal and amongst the most highly reactive elements on the periodic table. Rubidium has a density of about one and a half times that of water and is solid at room temperature, although it melts if it is just a bit warmer. It ignites spontaneously when it comes in contact with air and reacts violently with water and even with ice at -100 C, setting fire to the hydrogen that is liberated. Amongst all the other alkali metals, it forms amalgams with the element mercury. It alloys with gold, sodium, potassium and caesium. Its flame is yellowish-violet in colour. In this article, we will learn about Rb element in detail including rubidium element uses, structure, and chemical properties.

What is Rubidium?

Rubidium is a chemical element having the symbol Rb and the atomic number 37. It is an extremely soft, silvery-white coloured metal in the alkali metal group. The rubidium metal shares similarities to the potassium metal and the caesium metal when it comes to the physical appearance, softness and conductivity. It cannot be stored under atmospheric oxygen since a highly exothermic reaction would ensue, sometimes even resulting in the metal catching fire. It is the first alkali metal in the group having a density higher than water, hence it sinks, unlike the other metals that are above it in the group.

Rubidium Structure

The structure of rubidium is shown as below:

Let Us Now Look at the Chemical Properties of Rubidium

Chemical Properties of Rubidium

Rubidium symbol


Rubidium atomic number


Rubidium atomic mass

85.4678 g/mol

Group of rubidium


Period of rubidium


Block of rubidium


Melting point of Rb

39.30°C or 102.74°F or 312.45 K

Boiling point of rubidium

688°C or 1270°F or 961 K

Density of rubidium

1.53 g/cm3

Relative atomic mass of rubidium


Electronic configuration of rubidium

[Kr] 5s1

Key isotopes of rubidium

85Rb, 87Rb

Rubidium Uses

Rubidium has the following uses:

  1. Rubidium compounds are used in the fireworks for giving them a purple colour.

  2. Rubidium is used in the thermoelectric generator by using the magnetohydrodynamic principle, wherein the hot rubidium ions are allowed to pass through a magnetic field. 

  3. Vaporized rubidium, which is 87Rb, is one of the most commonly used atomic species for the laser cooling and the Bose-Einstein condensation.

  4. For cold-atom applications that require tunable interactions, 85Rb is preferable because of its rich Feshbach spectrum.

  5. Rubidium is also used for polarizing Helium-3 gas.

  6. The resonant element in the atomic clocks utilizes the hyperfine structure of the rubidium's energy levels, and hence, rubidium is used for high-precision timing.

  7. Rubidium is used as the main component of secondary frequency references or rubidium oscillators in the cell site transmitters and several other electronic transmitting, networking, and testing equipment.

  8. It is used as a working fluid in vapour turbines, as a getter in vacuum tubes, and as a component of the photocell.

  9. Rubidium is used as an ingredient in a special type of glass, production of superoxide by burning in oxygen, the study of potassium ion channels in biology, and as the vapour in the atomic magnetometers.

  10. Rubidium-82 is used for the positron emission tomography.

FAQ (Frequently Asked Questions)

1. What is the Chemical Name of Rb?

The Rb chemical name is rubidium, which is a chemical element having the symbol Rb and atomic number 37. It is a soft and silvery-white metal that lies in the alkali metal group.

2. What is the Atomic Number of Rubidium?

The atomic number of rubidium is 37. It is a part of the alkali metals group in the period 5 and block s.

3. What is Rubidium Used for in Everyday Life?

Rubidium is often used in everyday life. Rubidium and its salts have a few commercial uses as well. Given below are the uses of rubidium in the day to day life.

  1. The rubidium metal is used for manufacturing photocells and for removing the residual gases from vacuum tubes. 

  2. Rubidium salts are often used in glasses and ceramics. 

  3. Rubidium is used in the fireworks and gives them a purple colour. 

  4. Potential uses of rubidium are in the ion engines for space vehicles, as a working fluid in vapour turbines, and as a getter in the vacuum tubes.