NO. 069Lanthanide

Tm

Thulium

Thulium is the least abundant lanthanide and is used in portable X-ray devices.

Crystal Structure

Hexagonal close-packed (hcp)

Atomic Mass168.93 u

Density9.32 g/cm³

Melting Point1818 K

Boiling Point2223 K

Atomic Radius172 pm

Electronegativity1.25

Ionization Energy597 kJ/mol

Electron Affinity50 kJ/mol

Bonding TypeMetallic

Oxidation States3

Acid/BaseBasic

ReactivityMedium

Electron Configuration

[Xe] 4f13 6s2

Discovered ByPer Teodor Cleve

Year1879

Known Isotopes

Tm-169