Erbium (Er)

Stable isotopes of erbium available from ISOFLEX

Isotope Z(p) N(n) Atomic Mass Natural Abundance Enrichment Level Chemical Form
Er-162  68  94  161.928775 0.14% 28.20-39.20%  Oxide
Er-164  68  96  163.929197 1.61% 51.30-75.30%  Oxide
Er-166  68  98  165.930290 33.60% 94.70-98.10%  Oxide
Er-167  68  99  166.932046 22.95% 95.30-96.30% Oxide
Er-168  68  100  167.932368 26.80% >98.00% Oxide
Er-170  68  102  169.935461 14.90% 97.70-98.20%  Oxide

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Erbium was discovered in 1842 by Carl G. Mosander. It is named for the village of Ytterby, near Vaxholm, Sweden.

A soft, malleable solid with metallic luster, erbium has hexagonal, close-packed crystals. Its salts are pink to red, while it forms a dark-grey powder. In lump form, the metal is stable at ordinary temperatures, and it ignites in air in its finely-divided state. It has an effective magnetic moment of 9.9 Bohr magnetons at 25 ºC (it is paramagnetic, changing to antiferromagnetic at -189 ºC and to ferromagnetic at -253 ºC). It is insoluble in water and soluble in acids. In aqueous solution, erbium is always trivalent, Er3+. It forms water-insoluble trivalent salts; evaporation of solutions generally yields hydrated salts. The metal reacts with acids, forming corresponding salts and liberating hydrogen. When heated in oxygen or air, the metal (in lump form) slowly oxidizes, forming erbium sesquioxide.

Erbium's principal uses involve its pink-colored Er3+ ions, which have optical fluorescent properties that are useful in certain laser applications. Erbium-doped glasses or crystals can be used as optical amplification media. Erbium ion emissions are also helpful in laser surgery and in certain types of laser dentistry. Erbium is also used as a photographic filter and a metallurgic additive. It can be used as a colorant for glass, cubic zirconia and porcelain. It is used in neutron-absorbing control rods, cryocoolers and (in salt form) to help stimulate metabolism in humans.

Properties of Erbium

Name Erbium 
Symbol Er 
Atomic number 68 
Atomic weight 167.26 
Standard state Solid at 298 ºK 
CAS Registry ID 7440-52-0 
Group in periodic table N/A 
Group name Lanthanoid 
Period in periodic table 6 (Lanthanoid) 
Block in periodic table f-block 
Color Silvery white 
Classification Metallic 
Melting point 1529 °C
Boiling point 2863 °C
Vaporization point 2863 ºC
Thermal conductivity 14.5 W/(m·K) at 298.2 °K
Electrical resistivity 107.0 µΩ·cm at 25 °C; 205 µΩ·cm at 1000 ºC 
Electronegativity 1.2 
Specific heat 0.168 J/g mol at 20 °C 
Heat of vaporization 285 kJ·mol-1
Heat of fusion 19.9 kJ·mol-1
Density of liquid 8.86 g/cm3
Density of solid 9.07 g/cm3
Electron configuration [Xe]4f115d16s2
Atomic radius  1.758 Å (coordination number 12)
Atomic volume 18.49 cm3/mol
Oxidation states  +2, +3 

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