Terbium Properties (25 Facts You Should Know)

Terbium is an element of the lanthanide series which is rare due to its unavailability in the free state. Let us study various facts related to it as illustrated in the article.

Terbium is a silvery white, malleable, and ductile rare earth element that is found inclusively in the minerals cerite and monazite. Being electropositive in nature, it can easily show excellent reactivity, a feature uncommon to lanthanide series. 

Terbium is an element of value because it is expensive and now easy to obtain because of which it has few commercial purposes in semiconductor and fuel-based industries. Let us discuss more of its properties like electronegativity, ionization, magnetism, etc.

Terbium symbol

The symbol assigned to terbium is Tb.

terbium properties
Representation of terbium symbol and atom

Terbium group in the periodic table

There is no group assigned to terbium in the periodic table because it belongs to the lanthanide group situated below the main group periodic table.

Terbium period in the periodic table

Terbium is situated in the 6th period of the periodic table and is called the inner transition elements.

Terbium block in the periodic table

Terbium is present in the f-block of the periodic table and is part of the lanthanide series.

Terbium atomic number

The atomic number of terbium is 65.

Terbium atomic weight

The exact atomic weight of terbium is 158.92535 u.

Terbium electronegativity according to Pauling

The electronegativity of terbium according to the Pauling scale is 1.2 which is intermediate in the scale.

Terbium atomic density

The atomic density of terbium at room temperature is 8.23 g/cm3.

Terbium melting point

The melting point of terbium is 1356 degree Celsius which is quite high for the conversion of solid-state terbium to liquid.

Terbium boiling point     

The boiling point of terbium is 3230-degree Celsius which like its melting point is quite high explaining the rigidity of the element when it comes to the state of the matter.

Terbium Vanderwaals radius

The Van der Waals radius of terbium is 287 pm.

Terbium ionic/covalent radius

The covalent radius of the terbium is 194 pm with an error of +5 or -5.

Terbium isotopes

Isotopes have the same atomic position in the periodic table but are different in the number of neutrons. Let us find out and discuss various isotopes of terbium.

Terbium has 36 radioisotopes and 27 nuclear isomers (type of isotopes) which have diverse decay modes and half-lives. The most common and stable isotopes of terbium are:

  • 157Tb (71 years)
  • 158Tb (180 years)
  • 159Tb (Stable, does not decay)

Terbium electronic shells

Electronic shells are like orbits that are surrounded by the nucleus giving a broader perspective to electron distribution. Let us discuss it for terbium.

Terbium has 6 electron shells according to its atomic number. The division of electrons according to the octet rule is 2, 8, 18, 27, 8, 2.

Terbium energy of first ionization

The energy of the first ionization of terbium is 565.8 which is quite low as it is easy to remove the first electron.

Terbium energy of second ionization

The energy of the second ionization of terbium is 1110 KJ/mol which is higher as compared to Ist due to the stability issues.

Terbium energy of third ionization            

The energy of the third ionization of terbium is 2114 KJ/mol which increases exponentially due to increased nuclear attractions.

Terbium oxidation states

The common oxidation states of terbium are 0, +1, +2, +3, and +4. The +3-oxidation state is the most common and stable responsible for forming basic oxides. The rest of the oxidation states are unstable in water.

Terbium electron configuration

The electron configuration of terbium is [Xe]4f96s2 under rare earth elements where Xe is the xenon noble gas.

Terbium CAS number

The CAS number of terbium is 7440-27-9.

Terbium ChemSpider ID

The ChemSpider ID of terbium is 22397.

Terbium allotropic forms

Allotropic forms exhibit the existence of various crystalline forms of the same element with the same chemical properties. Let us find out the allotropic forms of terbium.

Terbium has 3 crystal allotropic forms which are classified based on temperature and magnetic ordering. The classification accordingly is:

  • Below 219K- Ferromagnetic ordering
  • Between 219K to 230K – Helical-antiferromagnetic
  • Above 230K – disordered diamagnetism

Terbium chemical classification

The chemical properties associated with terbium are:

  • Terbium is an electropositive element and can undergo easy oxidation.
  • Various oxides of terbium show fluorescence and photoluminescence.
  • Terbium has no biological role and can cause digestive issues or irritation when in contact with the skin and eyes.
  • Terbium can undergo complexation with 9 water molecules and can act as a chelating agent.

Terbium state at room temperature

Terbium is a solid lanthanide at room temperature under standard temperature and pressure conditions.

Is Terbium paramagnetic?

Magnetism exhibited by elements is highly influenced by atomic configurations and external environmental conditions. Let us check the same for the terbium.

Terbium is a diamagnetic element because of its filled stable 6s configuration but at a temperature of 300K, it is paramagnetic.


In nutshell, terbium is an expensive and rare earth element that has good reactivity with other elements due to its electropositive nature and has commercial uses as semiconductors, fuel cells and lasers.