chemicalelements.info

Thulium

69
Tm
Thulium
168.93

Properties

Symbol:Tm
Atomic Number:69
Atomic Weight:168.93
Density:9.32 g/cm3
Melting Point:
1818K
1545°C
2813°F
Boiling Point:
2223K
1950°C
3542°F

Electron Shells

2, 8, 18, 31, 8, 2

Thulium (Er) is a chemical element with atomic number 69. It belongs to the so called rare earth metals. The Earth's crust contains only about 0.5ppm (parts per million) of thulium, meaning 0.5 milligram per kg.

The only naturally occurring thulium isotope is 169Tm, with 69 protons and 100 neutrons.

Thulium emits a blue light when exposed to UV radiation. Because of this, thulium is being used in the Euro bank notes to prevent counterfeiting.