|Appearance||silvery bluish-gray metallic|
|Standard atomic weight (Ar, standard)||112.414(4)|
|Cadmium in the periodic table|
|Atomic number (Z)||48|
|Element category||post-transition metal, alternatively considered a transition metal|
|Electron configuration||[Kr] 4d10 5s2|
Electrons per shell
|2, 8, 18, 18, 2|
|Phase at STP||solid|
|Melting point||594.22 K (321.07 °C, 609.93 °F)|
|Boiling point||1040 K (767 °C, 1413 °F)|
|Density (near r.t.)||8.65 g/cm3|
|when liquid (at m.p.)||7.996 g/cm3|
|Heat of fusion||6.21 kJ/mol|
|Heat of vaporization||99.87 kJ/mol|
|Molar heat capacity||26.020 J/(mol·K)|
|Oxidation states||−2, +1, +2 (a mildly basic oxide)|
|Electronegativity||Pauling scale: 1.69|
|Atomic radius||empirical: 151 pm|
|Covalent radius||144±9 pm|
|Van der Waals radius||158 pm|
|Spectral lines of cadmium|
|Crystal structure||hexagonal close-packed (hcp)|
|Speed of sound thin rod||2310 m/s (at 20 °C)|
|Thermal expansion||30.8 µm/(m·K) (at 25 °C)|
|Thermal conductivity||96.6 W/(m·K)|
|Electrical resistivity||72.7 nΩ·m (at 22 °C)|
|Magnetic susceptibility||−19.8·10−6 cm3/mol|
|Young's modulus||50 GPa|
|Shear modulus||19 GPa|
|Bulk modulus||42 GPa|
|Brinell hardness||203–220 MPa|
|Discovery and first isolation||Karl Samuel Leberecht Hermann and Friedrich Stromeyer (1817)|
|Named by||Friedrich Stromeyer (1817)|
|Main isotopes of cadmium|
Cadmium forms chemical compounds in two oxidation states: +1 and +2. The +1 state is rare and unstable. The +2 state is much more common. Most +2 compounds dissolve easily in water and are white to yellow. Cadmium oxide can be brown, red, or white. Cadmium sulfide is bright yellow. Cadmium chloride and cadmium sulfate are colorless solids that dissolve easily in water. Cadmium fluoride is slightly soluble. Cadmium compounds are toxic when inhaled.
- Cadmium bromide, pale yellow solid, dissolves in water
- Cadmium chloride, colorless solid, dissolves in water
- Cadmium fluoride, gray solid, does not dissolve good in water
- Cadmium iodide, pale yellow solid, dissolves in water
- Cadmium oxide, white, brown, or red solid, dissolves in acids
- Cadmium sulfate, colorless solid, dissolves in water
- Cadmium sulfide, bright yellow solid, does not dissolve in water
- Cadmium telluride, black solid, semiconductor
Cadmium was found by two chemists, German chemist Friedrich Stromeyer discovered it in 1817, and Karl Herman also discovered it in 1818. They were looking at an impurity in zinc carbonate and found cadmium. For about 100 years, Germany made most cadmium. Cadmium iodide was used as a medicine although it was toxic.
Cadmium ores are rare. Greenockite, a cadmium sulfide mineral is the only main ore and it is found with sphalerite, a zinc sulfide. Because of this, most cadmium comes from zinc processing. Cadmium as a metal is very rare but is found in one place in Russia.
China makes the most cadmium. South Korea and Japan also make cadmium. Cadmium is taken from the zinc metal by heating the zinc metal in a vacuum. Cadmium is boiled first. The cadmium is condensed and used. Cadmium is also taken by precipitating it from the solution of zinc sulfate used to make pure zinc by electrolysis.
Now, cadmium is mainly used in nickel cadmium batteries. 86% of cadmium is used in batteries as of 2009. Some people are trying to stop using nickel-cadmium batteries because cadmium is toxic. Cadmium is still used to electroplate steel to prevent corrosion. Only about 6% of cadmium is used for this. Cadmium is also used in lasers, nuclear reactors, phosphors, photoresistors, pigments, and semiconductors. Wood's metal, an alloy that melts very easily, has cadmium in it. Cadmium is used in some solder.
Cadmium is not used in the human body or any other animal. A diatom uses cadmium, though.
Cadmium is a highly toxic metal. Dust of cadmium or its compounds is very dangerous and can kill. Some countries have banned cadmium from electronics. Cigarette smoking is the most important source of cadmium. Smokers have about 4 times more cadmium in their blood than nonsmokers (people who do not smoke). Cadmium is thought to be carcinogenic, although people still debate whether it is other things with the cadmium that cause cancer, like arsenic.
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