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Inorganic Chemistry

Pseudobinary Ionic Compound

Definition and meaning of Pseudobinary Ionic Compound in chemistry.

A pseudobinary ionic compound is a compound composed of more than two elements, but which behaves structurally or chemically like a simple binary compound composed of only two elements. This usually occurs when complex polyatomic ions act as single, discrete units that mimic monoatomic ions.

In more detail

In these materials, a polyatomic ion such as cyanide (CN-) or ammonium (NH4+) assumes the role of a single atom within the crystal lattice. The resulting structure often mirrors the simple crystal packing found in true binary salts like sodium chloride. Studying pseudobinary compounds helps chemists understand how complex ions influence lattice energy and crystal geometry. These compounds demonstrate how strong covalent bonds within a polyatomic ion allow it to remain intact during physical and chemical changes.

Key facts

FieldInorganic Chemistry
ComponentsPolyatomic ions acting as single units
StructureMimics binary lattices
Formula ExampleNH4Cl
Example

Ammonium chloride (NH4Cl) is a pseudobinary ionic compound because the ammonium polyatomic cation behaves like a single monoatomic alkali metal cation within the simple cubic crystal structure.

Frequently asked questions

What is the difference between a binary and pseudobinary compound?

A binary compound has exactly two elements, while a pseudobinary compound has three or more elements grouped into two functioning units.

Are pseudohalogens related to this?

Yes, pseudohalogen ions like cyanide often form the anion part of pseudobinary compounds.

Related terms