69
Tm
Thulium
169
Thulium (Tm)
LanthanidePeriod 6f-block-block
Thulium is a chemical element with symbol Tm and atomic number 69. It is the thirteenth and antepenultimate (third-last) element in the lanthanide series. Like the other lanthanides, the most common oxidation state is +3, seen in its oxide, halides and other compounds.
Latin name: Thulium
Atomic Number
69
Atomic Mass
169 g/mol
Phase (STP)
Solid
Electron Config.
[Xe] 4f¹³ 6s²
General
SymbolTm
Atomic Number69
Atomic Mass169 g/mol
CategoryLanthanide
Period6
Blockf-block
Electron Configuration[Xe] 4f¹³ 6s²
Valence Electrons15
Coloursilvery-gray metallic
Appearancesilvery gray
CAS NumberCAS7440-30-4
Physical Properties
Phase (STP)Solid
Density9.32 g/cm³
Melting Point1544.85°C · 2812.73°F · 1818.00 K
Boiling Point1949.85°C · 3541.73°F · 2223.00 K
Atomic Properties
Atomic Radius227 pm
Electronegativity1.25 Pauling
Ionization Energy597 kJ/mol
Oxidation States+3
Ion ChargeTm3+
Thermodynamic
Molar Heat27.03 J/(mol·K)
Crystal Structure
Crystal Structurehexagonal close-packed
Mechanical Properties
Mohs Hardness6
Nuclear & Hazards
Half-lifestable (Tm-169)
Abundance
In Universe0.000015%
In Sun0.000012%
In Earth's Crust0.0056%
In Meteorites0.00005%
Discovery & History
Discovery Year1879
Discovered ByPer Teodor Cleve
Country of DiscoverySweden
Isotopes of Thulium
| Isotope | Abundance | Half-life | Decay |
|---|---|---|---|
| Tm-169 | 100% | Stable | — |