Cadmium iodide

Cadmium iodide is the inorganic compound with the formula CdI2. It is a white hygroscopic solid. It also can be obtained as a mono- and tetrahydrate.[2] It has few applications. It is notable for its crystal structure, which is typical for compounds of the form MX2 with strong polarization effects.

Cadmium iodide
Cadmium iodide
Cadmium iodide
Names
IUPAC name
Cadmium(II) iodide
Other names
Cadmium diiodide
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.029.294
EC Number
  • 232-223-6
UNII
  • InChI=1S/Cd.2HI/h;2*1H/q+2;;/p-2 checkY
    Key: OKIIEJOIXGHUKX-UHFFFAOYSA-L checkY
  • InChI=1/Cd.2HI/h;2*1H/q+2;;/p-2
    Key: OKIIEJOIXGHUKX-NUQVWONBAZ
  • [Cd+2].[I-].[I-]
Properties
CdI2
Molar mass 366.22 g/mol
Appearance white to pale yellow crystals
Density 5.640 g/cm3, solid
Melting point 387 °C (729 °F; 660 K)
Boiling point 742 °C (1,368 °F; 1,015 K)
787 g/L (0 °C)
847 g/L (20 °C)
1250 g/L (100 °C)
Solubility soluble in ethanol, acetone, ether and ammonia
-117.2·10−6 cm3/mol
Structure
Trigonal, hP3, space group P3m1, No. 164
octahedral
Hazards
GHS labelling:
GHS06: ToxicGHS08: Health hazardGHS09: Environmental hazard
Danger
H301, H331, H351, H373, H410
P260, P280, P301+P330+P331, P304+P340, P310, P311, P403+P233
NFPA 704 (fire diamond)
NFPA 704 four-colored diamond
3
0
0
NIOSH (US health exposure limits):
PEL (Permissible)
 [1910.1027] TWA 0.005 mg/m3 (as Cd)[1]
REL (Recommended)
 Ca[1]
IDLH (Immediate danger)
 Ca [9 mg/m3 (as Cd)][1]
Related compounds
Other anions
 cadmium fluoride
cadmium chloride
cadmium bromide
Other cations
 zinc iodide
mercury(II) iodide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Preparation

Cadmium iodide is prepared by the addition of cadmium metal, or its oxide, hydroxide or carbonate to hydroiodic acid. Also, the compound can be made by heating cadmium with iodine.[2]

Crystal structure
The iodide anions in CdI2 form a hexagonal close-packed lattice, while the cadmium cations occupy all of the octahedral holes in alternating layers.

In cadmium iodide the iodide anions form a hexagonal close packed arrangement while the cadmium cations fill all of the octahedral sites in alternate layers. 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.[3]

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:

References
  1. NIOSH Pocket Guide to Chemical Hazards. "#0087". National Institute for Occupational Safety and Health (NIOSH).
  2. F. Wagenknecht; R. Juza (1963). "Cadmium iodide". In G. Brauer (ed.). Handbook of Preparative Inorganic Chemistry, 2nd Ed. Vol. 2. NY, NY: Academic Press. p. 1096.
  3. Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. pp. 1211–1212. ISBN 978-0-08-037941-8.
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