Cadmium iodide

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.

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
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 pictograms
GHS Signal word Danger
H301, H331, H351, H373, H400, H410
P260, P280, P301+330+331, P310, P304+340, P311, P403+233
NFPA 704 (fire diamond)
Flammability code 0: Will not burn. E.g. waterHealth code 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
0
3
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.

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.[2]

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. 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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