Cadmium

Cadmium is a chemical element; it has symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Like zinc, it demonstrates oxidation state +2 in most of its compounds, and like mercury, it has a lower melting point than the transition metals in groups 3 through 11. Cadmium and its congeners in group 12 are often not considered transition metals, in that they do not have partly filled d or f electron shells in the elemental or common oxidation states. The average concentration of cadmium in Earth's crust is between 0.1 and 0.5 parts per million (ppm). It was discovered in 1817 simultaneously by Stromeyer and Hermann, both in Germany, as an impurity in zinc carbonate.

Cadmium, ₄₈Cd

Cadmium
Pronunciation	/ˈkædmiəm/ ​(KAD-mee-əm)
Appearance	silvery bluish-gray metallic
Standard atomic weight Ar°(Cd)
	112.414±0.004 112.41±0.01 (abridged)
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 silver ← cadmium → indium
Atomic number (Z)	48
Group	group 12
Period	period 5
Block	d-block
Electron configuration	[Kr] 4d10 5s2
Electrons per shell	2, 8, 18, 18, 2
Physical properties
Phase at STP	solid
Melting point	594.22 K ​(321.07 °C, ​609.93 °F)
Boiling point	1040 K ​(767 °C, ​1413 °F)
Density (at 20° C)	8.649 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)
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)
Electronegativity	Pauling scale: 1.69
Ionization energies	1st: 867.8 kJ/mol 2nd: 1631.4 kJ/mol 3rd: 3616 kJ/mol
Atomic radius	empirical: 151 pm
Covalent radius	144±9 pm
Van der Waals radius	158 pm
Spectral lines of cadmium
Other properties
Natural occurrence	primordial
Crystal structure	​hexagonal close-packed (hcp) (hP2)
Lattice constants	a = 297.89 pm c = 561.66 pm (at 20 °C)
Thermal expansion	30.95×10−6/K (at 20 °C)
Thermal conductivity	96.6 W/(m⋅K)
Electrical resistivity	72.7 nΩ⋅m (at 22 °C)
Magnetic ordering	diamagnetic
Molar magnetic susceptibility	−19.8×10−6 cm3/mol
Young's modulus	50 GPa
Shear modulus	19 GPa
Bulk modulus	42 GPa
Speed of sound thin rod	2310 m/s (at 20 °C)
Poisson ratio	0.30
Mohs hardness	2.0
Brinell hardness	203–220 MPa
CAS Number	7440-43-9
History
Discovery and first isolation	Karl Samuel Leberecht Hermann and Friedrich Stromeyer (1817)
Named by	Friedrich Stromeyer (1817)
Isotopes of cadmium v e
Main isotopes Decay abun­dance half-life (t1/2) mode pro­duct 106Cd 1.25% stable 107Cd synth 6.5 h ε 107Ag 108Cd 0.89% stable 109Cd synth 462.6 d ε 109Ag 110Cd 12.5% stable 111Cd 12.8% stable 112Cd 24.1% stable 113Cd 12.2% 8.04×1015 y β− 113In 113mCd synth 14.1 y β− 113In IT 113Cd 114Cd 28.8% stable 115Cd synth 53.46 h β− 115In 116Cd 7.51% 2.8×1019 y β−β− 116Sn
Category: Cadmium view talk edit | references

Cadmium occurs as a minor component in most zinc ores and is a byproduct of zinc production. It was used for a long time in the 1900s as a corrosion-resistant plating on steel, and cadmium compounds are used as red, orange, and yellow pigments, to color glass, and to stabilize plastic. Cadmium's use is generally decreasing because it is toxic (it is specifically listed in the European Restriction of Hazardous Substances Directive) and nickel–cadmium batteries have been replaced with nickel–metal hydride and lithium-ion batteries. Due to it being a neutron poison, cadmium is also used as a component of control rods in nuclear fission reactors. One of its few new uses is in cadmium telluride solar panels.

Although cadmium has no known biological function in higher organisms, a cadmium-dependent carbonic anhydrase has been found in marine diatoms.