Thulium

Thulium (Tm)

Soft grey metallic element that belongs to the lanthanoids. One natural isotope exists, Tm-169, and seventeen artificial isotopes have been produced. No known uses for the element. Discovered in 1879 by Per Theodor Cleve.
Atomic Number69
Atomic Weight168.93422
Mass Number169
Group
Period6
Blockf
Protons69 p+
Neutrons100 n0
Electrons69 e-
Thulium sublimed dendritic and 1cm3 cube.jpg Animated Bohr Model Enhanced Bohr Model Bohr Model Orbital Diagram

Properties

Atomic Radius
175 pm
Atomic Volume
Covalent Radius
164 pm
Metallic Radius
Ionic Radius
103 pm
Crystal Radius
117 pm
Van der Waals radius
227 pm
Density
9.321 g/cm³
Boiling Point
2,220 K
Melting Point
1,818 K
Electrons per shell2, 8, 18, 31, 8, 2
Electronegativity
1.25
Electrophilicity
1.2616079623752 eV/particle
Proton Affinity
Electron Affinity
Ionization Potential
6.18431 eV/particle
Heat of Vaporization
232 kJ/mol
Heat of Fusion
Heat of Formation
232.2 kJ/mol
Molar Heat Capacity
27.03 J/(mol K)
Specific Heat Capacity
Thermal Conductivity
Gas Basicity
Dipole Polarizability
144 a₀
C6 Dispersion Coefficient
Oxidation States2, 3
Color
Silver
Crystal StructureSimple Hexagonal (HEX)
Lattice Constant
3.54 Å
Bulk Modulus
Electrical Resistivity
Electron Configuration[Xe] 4f13 6s2
Magnetic Ordering
Magnetic Susceptibility
PhaseSolid
Poisson Ratio
Shear Modulus
Young's Modulus
Allotropes
Alternate Names
Adiabatic Index
Appearance
Electric Conductivity
Critical Pressure
Critical Temperature
Curie Point
Electrical
Hardness
Magnetic Susceptibility
Magnetic
Neel Point
Neutron Cross Section
Neutron Mass Absorption
Gas Phase
Quantum Numbers
Refractive Index
Space Group
Speed of Sound
Superconducting Point
Thermal Expansion
Valence Electrons
Classification
CategoryLanthanides, Lanthanides
CAS Group
IUPAC Group
Glawe Number20
Mendeleev Number37
Pettifor Number22
Geochemical Classrare earth & related
Goldschmidt Classlitophile
Radioactivity
RadioactiveNo
Decay Mode
Half-Life
Lifetime
Abundance
Abundance in Earth's crust
0.52 mg/kg
Abundance in Oceans
0.00000017 mg/L
Abundance in Human Body
Abundance in Meteor
Abundance in Sun
Abundance in Universe1×10-8%

Isotopes of Thulium

Stable Isotopes
169Tm
Unstable Isotopes
145Tm 146Tm 147Tm 148Tm 149Tm 150Tm 151Tm 152Tm 153Tm 154Tm 155Tm 156Tm 157Tm 158Tm 159Tm 160Tm 161Tm 162Tm 163Tm 164Tm 165Tm 166Tm 167Tm 168Tm 170Tm 171Tm 172Tm 173Tm 174Tm 175Tm 176Tm 177Tm 178Tm 179Tm

History

Thulium was discovered by Swedish chemist Per Teodor Cleve in 1879 by looking for impurities in the oxides of other rare earth elements. The first researcher to obtain nearly pure thulium was Charles James, a British expatriate working on a large scale at New Hampshire College in Durham. High-purity thulium oxide was first offered commercially in the late 1950s. Named after Thule, the earliest name for Scandinavia

DiscoverersPer Theodor Cleve
Discovery LocationSweden
Discovery Year1879
Name OriginFrom Thule ancient name of Scandinavia.
Thulium is considered to be non-toxic
Thulium ore occurs most commonly in China

Uses

Thulium is used to dope yttrium aluminum garnets used in lasers. It has also been used in high-temperature superconductors similarly to yttrium. Thulium has use in ferrites, ceramic magnetic materials that are used in microwave equipment. Thulium is used in euro banknotes for its blue fluorescence under UV light to defeat counterfeiters. Radioactive thulium is used to power portable x-ray machines, eliminating the need for electrical equipment.

Sources

Found with other rare earths in the minerals gadolinite, euxenite, xenotime, and monazite. Monazite is often 50% rare earth by weight and 0.007% thulium.