Discovered By: Per Teodor Cleve
Discovery year: 1879

The following table showing some properties of Thulium(Tm):

Table Example
Atomic number 69
Group n/a
Period 6
Block f
Electrons 69
Protons 69
Neutrons 100
Atomic weight 168.93422
Oxidation states +2, +3
Ionic charge Tm^3+


Table Example
Electrons per shell K2 L8 M18 N31 O8 P2
Electron configuration 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^6 5s^2 4d^10 5p^6 6s^2 4f^13
Atomic radius 222 pm
Covalent radius 190 pm
Boiling point 1950°C
Melting point 1545°C
Neel point 56 K
Phase Solid
Fusion heat 16.8 kJ.mol^-1
Thermal expansion 1.33*10^-5 K^-1


Table Example
Vaporization heat 250 kJ.mol^-1
Color Silver
Brinell hardness 471 MPa
Bulk modulus 45 GPa
Density 9321 kg.m^-3
Liquid density 8560 kg.m^-3
Mohs hardness 1.8
Molar volume 1.812+10^-5 m^3.mol^-1
Poisson ratio 0.21
Shear modulus 31 GPa


Table Example
Vickers hardness 520 MPa
Young's modulus 74 GPa
Electrical type Conductor
Magnetic type Paramagnetic
Resistivity 7*10^-7 Ohm.m
Curie point 25 K
Electronegativity 1.25
Valence 3
Electron affinity 50 kJ.mol^-1
First ionization energy 596.7 kJ.mol^-1
Radioactive No
Neutron cross section 105 barn