Crystal structure type

Brief description

Examples

Co-ordination number

Number of formula units per unit cell

Type AB

Rock salt (NaCl) type

It has fcc arrangement in which Cl^- ions occupy the corners and face centres of a cube while Na⁺ ions are present at the body and edge of  centres.

Halides of Li, Na, K, Rb, AgF, AgBr, NH₄Cl, NH₄Br, NH₄I etc.

Na⁺ = 6

Cl^- = 6

4

Zinc blende (ZnS) type

It has ccp arrangement in which S^2- ions form fcc and each Zn²⁺ ion is surrounded tetrahedrally by four S^2- ions and vice versa.

CuCl, CuBr, CuI, AgI, Be

Zn²⁺ = 4

S^2- = 4

4

Type AB₂

Fluorite (CaF₂) type

It has arrangement in which Ca²⁺ ions form fcc with each Ca²⁺ ions surrounded by 8 F^- ions and each F^- ions by 4Ca²⁺ ions.

BaF₂, BaCl₂, SrF₂, SrCl₂, CdF₂, PbF₂

Ca²⁺ = 8

F^- = 4

4

Antifluorite type

Here negative ions form the ccp arrangement so that each positive ion is surrounded by 4 negative ions and each negative ion by 8 positive ions

Na₂O 

Na⁺ = 4

O^2- = 8

4

Caesium chloride (CsCl) type

It has the bcc arrangement with  at the body centre and  ions at the corners of a cube or vice versa.

CsCl, CsBr, CsI, CsCN, TlCl, TlBr, TlI  and TlCN

Cs⁺ =8

Cl^- = 8

1