Caesium hydroxide
Encyclopedia
Caesium hydroxide is a chemical compound
consisting of an atom of caesium
and a hydroxide
group (also known as hydroxyl
). It is a powerful base
, much like other alkali metal hydroxides
such as sodium hydroxide and potassium hydroxide
. In fact, caesium hydroxide is powerful enough to quickly corrode through glass.
Due to its high reactivity, caesium hydroxide is extremely hygroscopic. Laboratory caesium hydroxide is typically a hydrate
.
It is an anisotropic etchant of silicon
, exposing octahedral
planes. This technique can form pyramids and regularly shaped etch pits for uses such as Microelectromechanical systems
. It is known to have a higher selectivity to etch highly p-doped silicon than the more commonly used potassium hydroxide
.
However, this compound is not usually used in experiments as the extraction of caesium is very expensive and the fact that it behaves very much like rubidium hydroxide
and potassium hydroxide
although it is more reactive than they are.
Caesium hydroxide can be obtained by the following chemical reaction:
The above reaction occurs explosively with enough force to shatter a Pyrex
beaker. Caesium metal will react with ice above −116 °C.
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
consisting of an atom of caesium
Caesium
Caesium or cesium is the chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-gold alkali metal with a melting point of 28 °C , which makes it one of only five elemental metals that are liquid at room temperature...
and a hydroxide
Hydroxide
Hydroxide is a diatomic anion with chemical formula OH−. It consists of an oxygen and a hydrogen atom held together by a covalent bond, and carrying a negative electric charge. It is an important but usually minor constituent of water. It functions as a base, as a ligand, a nucleophile, and a...
group (also known as hydroxyl
Hydroxyl
A hydroxyl is a chemical group containing an oxygen atom covalently bonded with a hydrogen atom. In inorganic chemistry, the hydroxyl group is known as the hydroxide ion, and scientists and reference works generally use these different terms though they refer to the same chemical structure in...
). It is a powerful base
Base (chemistry)
For the term in genetics, see base A base in chemistry is a substance that can accept hydrogen ions or more generally, donate electron pairs. A soluble base is referred to as an alkali if it contains and releases hydroxide ions quantitatively...
, much like other alkali metal hydroxides
Alkali hydroxide
The alkali hydroxides are a class of chemical compounds which are composed of an alkali metal cation and the hydroxide anion . The alkali hydroxides are:*Lithium hydroxide *Sodium hydroxide *Potassium hydroxide...
such as sodium hydroxide and potassium hydroxide
Potassium hydroxide
Potassium hydroxide is an inorganic compound with the formula KOH, commonly called caustic potash.Along with sodium hydroxide , this colorless solid is a prototypical strong base. It has many industrial and niche applications. Most applications exploit its reactivity toward acids and its corrosive...
. In fact, caesium hydroxide is powerful enough to quickly corrode through glass.
Due to its high reactivity, caesium hydroxide is extremely hygroscopic. Laboratory caesium hydroxide is typically a hydrate
Hydrate
Hydrate is a term used in inorganic chemistry and organic chemistry to indicate that a substance contains water. The chemical state of the water varies widely between hydrates, some of which were so labeled before their chemical structure was understood....
.
It is an anisotropic etchant of silicon
Silicon
Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...
, exposing octahedral
Octahedron
In geometry, an octahedron is a polyhedron with eight faces. A regular octahedron is a Platonic solid composed of eight equilateral triangles, four of which meet at each vertex....
planes. This technique can form pyramids and regularly shaped etch pits for uses such as Microelectromechanical systems
Microelectromechanical systems
Microelectromechanical systems is the technology of very small mechanical devices driven by electricity; it merges at the nano-scale into nanoelectromechanical systems and nanotechnology...
. It is known to have a higher selectivity to etch highly p-doped silicon than the more commonly used potassium hydroxide
Potassium hydroxide
Potassium hydroxide is an inorganic compound with the formula KOH, commonly called caustic potash.Along with sodium hydroxide , this colorless solid is a prototypical strong base. It has many industrial and niche applications. Most applications exploit its reactivity toward acids and its corrosive...
.
However, this compound is not usually used in experiments as the extraction of caesium is very expensive and the fact that it behaves very much like rubidium hydroxide
Rubidium hydroxide
Rubidium hydroxide is a strong basic chemical and alkali that is formed by one rubidium ion and one hydroxide ion.Rubidium hydroxide does not appear in nature. However it can be obtained by synthesis from rubidium oxide...
and potassium hydroxide
Potassium hydroxide
Potassium hydroxide is an inorganic compound with the formula KOH, commonly called caustic potash.Along with sodium hydroxide , this colorless solid is a prototypical strong base. It has many industrial and niche applications. Most applications exploit its reactivity toward acids and its corrosive...
although it is more reactive than they are.
Caesium hydroxide can be obtained by the following chemical reaction:
- 2 Cs + 2 H2O → 2 CsOH + H2
The above reaction occurs explosively with enough force to shatter a Pyrex
Pyrex
Pyrex is a brand name for glassware, introduced by Corning Incorporated in 1915.Originally, Pyrex was made from borosilicate glass. In the 1940s the composition was changed for some products to tempered soda-lime glass, which is the most common form of glass used in glass bakeware in the US and has...
beaker. Caesium metal will react with ice above −116 °C.