Cadmium

General

Name	Cadmium	Symbol	Cd
Atomic number	48	Atomic weight	112.41
Density @ 293 K	8.65 g/cm3	Atomic volume	13.1 cm3/mol
Group	Trans. Met.	Discovered	1817

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States

State (s, l, g)	s
Melting point	594.1 K	Boiling point	1038 K
Heat of fusion	6.192 kJ/mol	Heat of vaporization	99.570 kJ/mol

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Energies

1st ionization energy	867.7 kJ/mole	Electronegativity	1.69
2nd ionization energy	1631.4 kJ/mole	Electron affinity	kJ/mole
3rd ionization energy	3616.2 kJ/mole	Specific heat	0.23 J/gK
Heat atomization	112 kJ/mole atoms

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Oxidation & Electrons

Shells	2,8,18,18,2	Electron configuration	[Kr] 4d10 5s2
Minimum oxidation number	0	Maximum oxidation number	2
Minimum common oxidation no.	0	Maximum common oxidation number	2

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Appearance & Characteristics

Structure	distorted hcp structure	Color	bluish-white
Uses	battery,yel. pigment(CdS)	Toxicity
Hardness	2 mohs	Characteristics	soft

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Reactions

Reaction with air	mild, w/ht =>CdO	Reaction with 6M HCl	mild, =>H2, Cd(Cl)2
Reaction with 6M HCl	mild, =>H2, Cd(Cl)2	Reaction with 15M HNO3	mild, =>Cd(NO3)2, NOx
Reaction with 6M NaOH	none

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Other Forms

Number of isotopes		8	Hydride(s)
Oxide(s)		CdO	Chloride(s)		CdCl2

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Radius

Ionic radius (2- ion)	pm	Ionic radius (1- ion)	pm
Atomic radius	151 pm	Ionic radius (1+ ion)	pm
Ionic radius (2+ ion)	109 pm	Ionic radius (3+ ion)	pm

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Conductivity

Thermal conductivity		96.9 J/m-sec-deg	Electrical conductivity		146.413 1/mohm-cm
Polarizability		7.2 A^3

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HOME

Source	Sphalerite (sulfide)	Rel. abund. solar system	0.207 log
Abundance earth's crust	-0.7 log	Cost, pure	6 $/100g
Cost, bulk	$/100g

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History:

(L. cadmia; Gr. kadmeia - ancient name for calamine, zinc carbonate) Discovered by Stromeyer in 1817 from an impurity in zinc carbonate. Cadmium most often occurs in small quantities associated with zinc ores, such as sphalerite (ZnS). Greenockite (CdS) is the only mineral of any consequence bearing cadmium. Almost all cadmium is obtained as a by-product in the treatment of zinc, copper, and lead ores. It is a soft, bluish-white metal which is easily cut with a knife. It is similar in many respects to zinc. It is a component of some of the lowest melting alloys; it is used in bearing alloys with low coefficients of friction and great resistance to fatigue; it is used extensively in electroplating, which accounts for about 60% of its use. It is also used in many types of solder, for standard E.M.F. cells, for Ni-Cd batteries, and as a barrier to control nuclear fission. Cadmium compounds are used in black and white television phospros and in blue and green phosphors for color TV tubes. It forms a number of salts, of which the sulfate is most common; the sulfide is used as a yellow pigment. Cadmium and solutions of its compounds are toxic. Failure to appreciate the toxic properties of cadmium may cause workers to be unwittingly exposed to dangerous fumes. Silver solder, for example, which contains cadmium, should be handled with care. Serious toxicity problems have been found from long-term exposure and work with cadmium plating baths. Exposure to cadmium dust should not exceed 0.01 mg/m^3 (8-hour time-weighted average, 40-hour week). The ceiling concentration (maximum), for a period of 15 min, should not exceed 0.14 mg/m^3. Cadmium oxide fume exposure (8-hour, 40-hour week) should not exceed 0.05 mg/m^3, and the maximum concentration should not exceed 0.05 mg/m^3. These values are presently being restudied and recommendations have been made to reduce the exposure. In 1927 the International Conference on Weights and Measures redefined the meter in terms of the wavelength of the red cadmium spectral line (i.e. 1m = 1.553,164.13 wavelengths). This definition has been changed (see under Krypton). The current price of cadmium is about $12/lb. It is available in high purity form.

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