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Cadmium iodide

Cadmium iodide
IUPAC name cadmium(II) iodide
Other names cadmium iodide
cadmium diiodide
CAS number 7790-80-9
Molecular formula CdI2
Molar mass 366.20 g mol−1
Appearance white to pale yellow crystals
Density 5.640 g cm−3, solid
Melting point

388°C (661 K)

Boiling point

787°C (1060 K)

Solubility in water  ? g/100 ml (?°C)
Crystal structure rhombohedral
NFPA 704
Related Compounds
Other anions cadmium fluoride
cadmium chloride
cadmium bromide
Other cations zinc iodide
mercury(II) iodide
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox disclaimer and references

Cadmium iodide, CdI2, is a chemical compound of cadmium and iodine. It is notable for its crystal structure, which is typical for compounds of the form MX2 with strong polarization effects.


Crystal structure

Cadmium iodide forms crystals with hexagonal symmetry. The iodide anions form a hexagonal close packed arrangement while the cadmium cations fill alternating layers of octahedral sites. The resultant structure consists of a layered lattice. This same basic structure is found in many other salts and minerals. Cadmium iodide is mostly ionically bonded but with partial covalent character.

Cadmium iodide's crystal structure is the prototype on which the crystal structures many other compounds can be considered to be based. Compounds with any of the following characteristics tend to adopt the CdI2 structure:

  • Iodides of moderately polarising cations; bromides and chlorides of strongly polarising cations
  • Hydroxides of dications, i.e. compounds with the general formula M(OH)2
  • Sulfides, selenides and tellurides (chalcogenides) of tetracations, i.e. compounds with the general formula MX2, where X = S, Se, Te

Compounds with the CdI2 crystal structure



MgI2, TiI2, VI2, MnI2, FeI2, CoI2, CaI2, PdI2, PbI2.

Chlorides and bromides

TiCl2, VCl2;

MgBr2, TiBr2, VBr2, MnBr2, FeBr2, CoBr2.

Hydroxides of M2+

Mg(OH)2, Ni(OH)2, Ca(OH)2.

Chalcogenides of M4+

TiS2, ZrS2, SnS2, α-TaS2, PtS2;

TiSe2, ZrSe2, SnSe2, PtSe2;

SiTe2, TiTe2, CoTe2, NiTe2, PdTe2, PtTe2.


Ag2F, W2C.


    1. N. N. Greenwood, A. Earnshaw, Chemistry of the Elements, 2nd ed., Butterworth-Heinemann, Oxford, UK, 1997.
    This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Cadmium_iodide". A list of authors is available in Wikipedia.
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