Element 69
Thulium
Lanthanides
Thulium (Tm) is in the f-block of the periodic table — group 3, period 6.
Thulium is a chemical element with symbol Tm and atomic number 69.
Key data
- Atomic number
- 69
- Atomic mass
- 168.934 u
- Group / Period
- 3 / 6
- Block
- f-block
- Phase at STP
- Solid
- Density
- 9.32 g/cm³
- Melting point
- 1544.8 °C
- Boiling point
- 1949.8 °C
- Electron configuration
- [Xe] 4f13 6s2
Periodic table block
Thulium is in the f-block (group 3, period 6). Elements land in the f-block when their highest-energy electrons fill an f subshell — these are the lanthanides and actinides shown beneath the main table.
New to this? Periodic table blocks explained: s, p, d, and f
Common uses
- •Portable X-ray sources
- •Lasers
- •Glassmaking
Discovery
Year: 1879
Discovered by: Per Teodor Cleve
Frequently asked questions
What is the atomic number of Thulium?
Thulium has atomic number 69. Its symbol is Tm and its atomic mass is 168.934 u.
What category of element is Thulium?
Thulium is classified as lanthanides. It sits in group 3, period 6 of the periodic table.
What block of the periodic table is Thulium in?
Thulium is in the f-block (group 3, period 6). Its highest-energy electrons occupy the f subshell — you can see this in its electron configuration, [Xe] 4f13 6s2.
What is Thulium used for?
Common uses of Thulium include: Portable X-ray sources, Lasers, Glassmaking.
When was Thulium discovered?
Thulium was discovered in 1879 by Per Teodor Cleve.
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