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Cadmium

chemical element with the atomic number of 48

Cadmium is a metal. It is element 48 on the periodic table. Its symbol is Cd. Its atomic number is 48 and its atomic mass is 112.4. It is found in Group 12 on the periodic table.[4]

Cadmium,  48Cd
Cadmium-crystal bar.jpg
General properties
Pronunciation/ˈkædmiəm/ (KAD-mee-əm)
Appearancesilvery bluish-gray metallic
Standard atomic weight (Ar, standard)112.414(4)[1]
Cadmium in the periodic table
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson
Zn

Cd

Hg
silvercadmiumindium
Atomic number (Z)48
Groupgroup 12
Periodperiod 5
Blockd-block
Element category  post-transition metal, alternatively considered a transition metal
Electron configuration[Kr] 4d10 5s2
Electrons per shell
2, 8, 18, 18, 2
Physical properties
Phase at STPsolid
Melting point594.22 K ​(321.07 °C, ​609.93 °F)
Boiling point1040 K ​(767 °C, ​1413 °F)
Density (near r.t.)8.65 g/cm3
when liquid (at m.p.)7.996 g/cm3
Heat of fusion6.21 kJ/mol
Heat of vaporization99.87 kJ/mol
Molar heat capacity26.020 J/(mol·K)
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 530 583 654 745 867 1040
Atomic properties
Oxidation states−2, +1, +2 (a mildly basic oxide)
ElectronegativityPauling scale: 1.69
Ionization energies
  • 1st: 867.8 kJ/mol
  • 2nd: 1631.4 kJ/mol
  • 3rd: 3616 kJ/mol
Atomic radiusempirical: 151 pm
Covalent radius144±9 pm
Van der Waals radius158 pm
Color lines in a spectral range
Spectral lines of cadmium
Other properties
Natural occurrenceprimordial
Crystal structurehexagonal close-packed (hcp)
Hexagonal close packed crystal structure for cadmium
Speed of sound thin rod2310 m/s (at 20 °C)
Thermal expansion30.8 µm/(m·K) (at 25 °C)
Thermal conductivity96.6 W/(m·K)
Electrical resistivity72.7 nΩ·m (at 22 °C)
Magnetic orderingdiamagnetic[2]
Magnetic susceptibility−19.8·10−6 cm3/mol[3]
Young's modulus50 GPa
Shear modulus19 GPa
Bulk modulus42 GPa
Poisson ratio0.30
Mohs hardness2.0
Brinell hardness203–220 MPa
CAS Number7440-43-9
History
Discovery and first isolationKarl Samuel Leberecht Hermann and Friedrich Stromeyer (1817)
Named byFriedrich Stromeyer (1817)
Main isotopes of cadmium
Iso­tope Abun­dance Half-life (t1/2) Decay mode Pro­duct
106Cd 1.25% stable
107Cd syn 6.5 h ε 107Ag
108Cd 0.89% stable
109Cd syn 462.6 d ε 109Ag
110Cd 12.47% stable
111Cd 12.80% stable
112Cd 24.11% stable
113Cd 12.23% 7.7×1015 y β 113In
113mCd syn 14.1 y β 113In
IT 113Cd
114Cd 28.75% stable
115Cd syn 53.46 h β 115In
116Cd 7.51% 3.1×1019 y ββ 116Sn
| references

PropertiesEdit

Physical propertiesEdit

Cadmium is a blue-gray soft metal. It can be considered a transition metal or a post-transition metal. It is malleable and ductile. It is similar to zinc. It melts at 321°C.

Cadmium has 8 natural isotopes. 5 are radioactive, but 3 have very long half-lives so their radioactivity is almost nothing.

Chemical propertiesEdit

Cadmium is a moderately reactive metal. It corrodes in moist air and dissolves in acids. It burns in air when powdered to make the brown cadmium oxide.

Chemical compoundsEdit

 
Cadmium chloride
 
Cadmium oxide

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.

HistoryEdit

Cadmium was found by two chemists, German chemist Friedrich Stromeyer discovered it in 1817, and Karl Herman also discovered it in 1818.[5] 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.

OccurrenceEdit

 
Greenockite (yellow crystal)

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.

PreparationEdit

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.[6]

UsesEdit

In the 1930s and 1940s cadmium was mainly used to plate steel to prevent it from corroding. Then cadmium sulfide was used as a pigment in paint.

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.

SafetyEdit

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.

ReferencesEdit

  1. Meija, J.; Coplen, T. B.; Berglund, M.; Brand, W.A.; De Bièvre, P.; Gröning, M.; Holden, N.E.; Irrgeher, J. et al. (2016). "Atomic weights of the elements 2013 (IUPAC Technical Report)". Pure and Applied Chemistry 88 (3): 265-91. doi:10.1515/pac-2015-0305. https://www.degruyter.com/downloadpdf/j/pac.2016.88.issue-3/pac-2015-0305/pac-2015-0305.xml. 
  2. Lide, D. R., ed. (2005). "Magnetic susceptibility of the elements and inorganic compounds". CRC Handbook of Chemistry and Physics (PDF) (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5.
  3. Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.
  4. The Element Cadmium: It's Elemental - The Element Cadmium, accessdate: February 19, 2016
  5. "Cadmium". Chemicool.com. 2016. Retrieved 19 February 2016.
  6. ELECTROLYTIC ZINC PRODUCTION: ELECTROLYTIC ZINC PRODUCTION, accessdate: February 19, 2016