Thulium (Tm)

Atomic Number: 69

Relative Atomic Mass: 168.93421

Electronegativity: 1.25

Atomic Radius (Picometers): 175

Appearance: Silver-Grey

Occurrence: Natural

Melting Point (Kelvin): 1818

Boiling Point (Kelvin): 2223

Stable Isotopes: 169

Discoverer: Per Teodor Cleve in 1879

Properties: Malleable, Soft, Ductile

First Use: Unknown

Modern Uses: Lasers, X-Ray Sources

Picture Courtesy of Alchemist-hp

©2011 Grant Dwyer