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Structure of Ionic Crystals

Structure of Ionic Crystals

Table: Types of ionic crystal with description

Crystal structure typeBrief description

Examples

Co-ordination numberNumber of formula units per unit cell

Type AB

Rock salt (NaCl) type

It has fcc arrangement in which ions occupy the corners and face centres of a cube while ions are present at the body and edge of centres.Halides of Li, Na, K, Rb, AgF, AgBr, NH4Cl, NH4Br, NH4I etc.

4

 

Zinc blende (ZnS) typeIt has ccp arrangement in which ions form fcc and each ion is surrounded tetrahedrally by four ions and vice versa.

4

Type AB2

Fluorite (CaF2) type

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

4
Antifluorite typeHere 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

4
Caesium chloride (CsCl) typeIt has the bcc arrangement with at the body centre and ions at the corners of a cube or vice versa. and

1

 

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