Thulium

Atomic number

69

Atomic mass (u)

168.93422

Category

Lanthanide

Standard state

Solid

Melting point

1544.85 °C (1818 K)

Boiling point

1949.85 °C (2223 K)

Density (g/cm³)

9.32

Electronegativity (Pauling)

1.25

Electron configuration

[Xe]6s2 4f13

Oxidation states

+3

Atomic radius (pm)

227

First ionization energy (eV)

6.184

Discovery & recognition

Discovery year / period (PubChem)

1879

Discovery credited to (RSC)

Per Teodor Cleve

Date or period recorded by RSC

1879

Discovery place

Uppsala, Sweden

An ancient date does not identify a first human discovery. Different references may date observation, isolation and formal recognition differently.

Natural occurrence & production

The creation of an element’s nuclei and its concentration into terrestrial deposits are different processes. The occurrence note below concerns its presence or production on Earth; it is not a complete account of nucleosynthesis.

“Thulium is found principally in the mineral monazite, which contains about 20 parts per million.”

Royal Society of Chemistry · occurrence excerpt ↗

Continue the research

Reference values are not product specifications. Blank values have not been estimated. For superheavy elements, some properties and family assignments are theoretical or incompletely measured.