Rubidium

Rubidium is a silvery white, metallic solid at room temperature.

Its symbol is Rb and the ground state electron configuration is [Kr]5s¹. It is also a member of the group 1 alkali metals and so is again an s-block element.

As you can see from the picture below the shell structure of Rubidium is 2.8.18.8.1 and so its atomic number is 37.

Production of Rubidium

Rubidium is produced by the reaction of metallic Sodium with hot molten Rubidium Chloride:

Na + RbCl ↔ Rb + NaCl

The method used to extract the Rubidium results in it being relatively free from sodium impurities.

Reactions of Rubidium...

...with air:-

A freshly cut segment of Rubidium has a bright and shiny surface. However, the longer this surface is exposed to the air the more it dulls due to it reacting with the oxygen and moisture in the air. When Rubidium is burned in air the result is the formation of a dark brown compound called Rubidium Superoxide:

Rb(s) + O₂(g) → RbO₂(s)

...with water:-

Rubidium reacts very rapidly with water and is extremely exothermic. It results in a colourless, basic solution due to the formation of Rubidium Hydroxide and Hydrogen gas. This reaction occurs so fast that if it was to take place in a glass vessel, the glass would end up shattered! This reaction is slower than that of Caesium with water.

2Rb(s) + 2H₂O → 2RbOH(aq) + H₂(g)

...with halogens:-

Rubidium reacts very strongly with all the halogens:

2Rb(s) + F₂(g) → 2RbF(s)

2Rb(s) + Cl₂(g) → 2RbCl(s)

2Rb(s) + Br₂(g) → 2RbBr(s)

2Rb(s) + I₂(g) → 2RbI(s)

These are all called Rubidium Halides.

Uses of Rubidium

Rubidium doesn't have very many uses. The most common are:-

• used in making special glasses
• can be used in ion propulsion systems
• as a component in a photocell

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