Cadmium iodide

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Cadmium iodide
General
Systematic name	cadmium(II) iodide
Other names	cadmium iodide cadmium diiodide
Chemical formula	CdI2
Molar mass	366.20 g mol−1
Appearance	white to pale yellow crystals
CAS number	[7790-80-9]
Properties
Density and phase	5.640 g cm−3, solid
Solubility in water	? g/100 ml (?°C)
Melting point	388°C (661 K)
Boiling point	787°C (1060 K)
Structure
Coordination geometry	octahedral
Crystal structure	rhombohedral
Dipole moment	? D
Hazards
MSDS	External MSDS
Main hazards	?
NFPA 704	0 2 0
Supplementary data page
Structure and properties	n, εr, etc.
Thermodynamic data	Phase behaviour Solid, liquid, gas
Spectral data	UV, IR, NMR, MS
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.

[edit] 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

[edit] Compounds with the CdI₂ crystal structure

The iodide anions in CdI₂ form a hexagonal close-packed structure, while the cadmium cations occupy some of the octahedral interstices

[edit] Iodides

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

[edit] Chlorides and bromides

TiCl₂, VCl₂;

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

[edit] Hydroxides of M²⁺

Mg(OH)₂, Ni(OH)₂, Ca(OH)₂.

[edit] Chalcogenides of M⁴⁺

TiS₂, ZrS₂, SnS₂, α-TaS₂, PtS₂;

TiSe₂, ZrSe₂, SnSe₂, PtSe₂;

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

[edit] Others

Ag₂F, W₂C.

[edit] References

1. N. N. Greenwood, A. Earnshaw, Chemistry of the Elements, 2nd ed., Butterworth-Heinemann, Oxford, UK, 1997.

[edit] External links

• Links to external chemical sources.

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