Name, Symbol, Number Erbium, Er, 68
Chemical series Lanthanides
Group, Period, Block NA, 6, f
Density, Hardness 9066 kg/m3, ND
Appearance silvery white
Atomic properties
Atomic weight 167.259 amu
Atomic radius (calc.) 175 (226) pm
Covalent radius ND pm
van der Waals radius ND pm
Electron configuration [Xe]6s²4f12
e- 's per energy level 2,8,18,30,8,2
Oxidation states (Oxide) 3 (basic)
Crystal structure Hexagonal
Physical properties
State of matter solid
Melting point 1795 K (2772 ?F)
Boiling point 3136 K (5185 ?F)
Molar volume ND ×10-6 m3/mol
Heat of vaporization 261 kJ/mol
Heat of fusion 17.2 kJ/mol
Vapor pressure ND
Velocity of sound 2830 m/s at 293.15 K
Electronegativity 1.24 (Pauling scale)
Specific heat capacity 170 J/(kg*K)
Electrical conductivity 1.17 106/m ohm
Thermal conductivity 14.3 W/(m*K)
1st ionization potential 589.3 kJ/mol
2nd ionization potential 1150 kJ/mol
3rd ionization potential 2194 kJ/mol
4th ionization potential 4120 kJ/mol
Most stable isotopes
iso NA half-life DM DE MeV DP
160Er {syn.} 28.58 h ε 0.330 160Ho
162Er 0.14% Erbium is stable with 94 neutrons
164Er 1.61% Erbium is stable with 96 neutrons
165Er {syn.} 10.36 h ε 0.376 165Ho
166Er 33.6% Erbium is stable with 98 neutrons
167Er 22.95% Erbium is stable with 99 neutrons
168Er 26.8% Erbium is stable with 100 neutrons
169Er {syn.} 9.4 d β- 0.351 169Tm
170Er 14.9% Erbium is stable with 102 neutrons
171Er {syn.} 7.516 h β- 1.490 171Tm
172Er {syn.} 49.3 h β- 0.891 172Tm
SI units & STP are used except where noted.

Erbium is a chemical element in the periodic table that has the symbol Er and atomic number 68. A rare silvery metallic lanthanide rare earth element, erbium is associated with several other rare elements in the mineral gadolinite from Ytterby in Sweden.

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Notable characteristics

A trivalent element, pure erbium metal is malleable, soft, somewhat stable in air and does not oxidize as quickly as some other rare-earth metals. Its salts are rose-colored and the element gives a characteristic sharp absorption spectra in visible light, ultraviolet, and near infrared. Otherwise it looks much like the other rare earths. Its sesquioxide is called erbia. Erbium's properties are to a degree dictated by the kind and amount of impurities present. Erbium does not play any known biological role but is thought by some to be able to stimulate metabolism.


Erbium's everyday uses are varied; commonly it is used as a photographic filter and because of its resilience it is useful as an metallurgical additive. Other uses:


Erbium (for Ytterby, a town in Sweden) was discovered by Carl Gustaf Mosander in 1843. Mosander separated "yttria" from the mineral gadolinite into three fractions which he called yttria, erbia, and terbia. He named the new element after the town of Ytterby where large concentrations of yttria and erbium are located. Erbia and terbia, however, were confused in at this time. After 1860, what had been known as terbia was renamed erbia and after 1877 what had been known as erbia was renamed terbia. Fairly pure Er2O3 was independently isolated in 1905 by Georges Urbain and Charles James. Reasonably pure metal wasn't produced until 1934 when workers reduced the anhydrous chloride with potassium vapor.


Like other rare earths, this element is never found as a free element in nature but is found bound monazite sand ores. It has historically been very difficult and expensive to separate rare earths from each other in their ores but ion-exchange production techniques developed in the late 20th century have greatly brought down the cost of production of all rare-earth metals and their chemical compounds. The principal commercial sources of erbium are from the minerals xenotime and euxenite. Metallic erbium in dust form presents a fire and explosion hazard.


Naturally occurring erbium is composed of 6 stable isotopes, Er-162, Er-164, Er-166, Er-167, Er-168, and Er-170 with Er-166 being the most abundant (33.6% natural abundance). 23 radioisotopes have been characterized, with the most stable being Er-169 with a half life of 9.4 days, Er-172 with a half-life of 49.3 hours, Er-160 with a half-life of 28.58 hours, Er-165 with a half-life of 10.36 hours, and Er-171 with a half life of 7.516 hours. All of the remaining radioactive isotopes have half-lifes that are less than 3.5 hours, and the majority of these have half lifes that are less than 4 minutes. This element also has 6 meta states, with the most stable being Er-167m (t? 2.269 seconds).

The isotopes of erbium range in atomic weight from 144.957 amu (Er-145) to 173.944 amu (Er-174). The primary decay mode before the most abundant stable isotope, Er-166, is electron capture, and the primary mode after is beta decay. The primary decay products before Er-166 are element 67 (holmium) isotopes, and the primary products after are element 69 (thulium) isotopes.


As with the other lanthanides, erbium compounds are of low to moderate toxicity, although their toxicity has not been investigated in detail.


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