Name: thulium
Symbol: Tm
Atomic number: 69
Atomic weight: 168.93421 (2)
Group in periodic table:
Group name: Lanthanoid
Period in periodic table: 6 (lanthanoid)
Block in periodic table: f-block
CAS registry ID: 7440-30-4
Thulium is the least abundant of the earth elements, and is about as rare as silver, gold, or cadmium.
The pure metal has a bright, silvery lustre. It is reasonably stable in air, but the metal must be protected from moisture. The element is silvery-grey, soft, malleable, and ductile, and can be cut with a knife. It is a rare earth metal found in minerals such as monazite.