Periodic Table


Atomic number: 65
Atomic weight: 158.92534
Symbol: Tb
Group number: (lanthanide)
Electronic configuration: [Xe].4f9.6s2


Terbium is reasonably stable in air. It is a silvery-grey metal, and is malleable, ductile, and soft enough to be cut with a knife. It is a rare earth metal found in cerite, gadolinite and monazite. The element itself was isolated only recently.

General information

Discoveror: Carl Mosander
Date discovered: 1843
Discovered at: Sweden
Meaning of name: Named after "Ytterby", a town in Sweden

Physical data

Standard state: solid at 298 K
Colour: silvery white
Density of solid at ambient temperature/kg m-3: 8219
Molar volume/cm3: 19.30

Radii /pm

Atomic: 225
Covalent (single bond):
Pauling radius for the ion [Tb]-: no data

Valence shell orbital radius maxima (Rmax)
orbital s p d f
radius209.3no datano data29.1


Both values are quoted on the Pauling scale.

Pauling: no data
Allred Rochow: 1.10

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: 1629
boiling point: 3503

Enthalpies /kJ mol-1

fusion: 10.5
vaporization: 293

single bond enthalpies:
Tb-F Tb-Cl Tb-Br Tb-I Tb-Tb
no data no data no data 339 131.4

Ionization enthalpies /kJ mol-1

Number Enthalpy


This section gives some data for naturally occurring isotopes.
Nominal mass Accurate mass % natural abundance
159Tb158.925342 (4)100

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/Tb.html