Periodic Table


Atomic number: 68
Atomic weight: 167.26
Symbol: Er
Group number: (lanthanide)
Electronic configuration: [Xe].4f12.6s2


Pure erbium metal is soft and malleable and has a bright, silvery, metallic lustre. As with other rare-earth metals, its properties depend to a certain extent on impurities present. The metal is fairly stable in air and does not oxidise as rapidly as some of the other rare-earth metals.

General information

Discoveror: Carl G. Mosander
Date discovered: 1842
Discovered at: Sweden
Meaning of name: Named after the village of "Ytterby" near Vauxholm in Sweden

Physical data

Standard state: solid at 298 K
Colour: silvery white
Density of solid at ambient temperature/kg m-3: 9066
Molar volume/cm3: 18.46

Radii /pm

Atomic: 226
Covalent (single bond):
Pauling radius for the ion [Er]-: no data

Valence shell orbital radius maxima (Rmax)
orbital s p d f
radius203.1no datano data26.8


Both values are quoted on the Pauling scale.

Pauling: 1.24
Allred Rochow: 1.11

Crystal Structure

structure: hcp (hexagonal close-packed)

The following CrystalMaker image represents the solid state structure. For most elements, the most stable allotrope is illustrated. Try WebElements version 2 for interactive virtual reality and CHIME images.


Temperatures (/K)

melting point: 1770
boiling point: 3141

Enthalpies /kJ mol-1

fusion: 19.9
vaporization: 286

single bond enthalpies:
Er-F Er-Cl Er-Br Er-I Er-Er
no data no data no data 310 no data

Ionization enthalpies /kJ mol-1

Number Enthalpy


This section gives some data for naturally occurring isotopes.
Nominal mass Accurate mass % natural abundance
162Er161.928775 (4)0.14 (1)
164Er163.929198 (4)1.61 (1)
166Er165.930290 (4)33.6 (2)
167Er166.932046 (4)22.95 (15)
168Er167.932368 (4)26.8 (2)
170Er169.935461 (4)14.9 (1)

Further Information

Copyright 1997 Mark Winter
Department of Chemistry at the University of Sheffield, Sheffield S3 7HF, England.

The current version of this document is at http://www.shef.ac.uk/~chem/web-elements-I/Er.html