Tm Thulium
Element Information, Facts, Properties, Trends, Uses, Comparison with other elements

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.
It belongs to group of the periodic table having trivial name .
Thulium Facts
Read key information and facts about element Thulium
Name | Thulium |
Atomic Number | 69 |
Atomic Symbol | Tm |
Atomic Weight | 168.93421 |
Phase | Solid |
Color | Silver |
Appearance | silvery gray |
Classification | Lanthanide |
Group in Periodic Table | - |
Group Name | |
Period in Periodic Table | period 6 |
Block in Periodic Table | f -block |
Electronic Configuration | [Xe] 4f13 6s2 |
Electronic Shell Structure (Electrons per shell) | 2, 8, 18, 31, 8, 2 |
Melting Point | 1818 K |
Boiling Point | 2223 K |
CAS Number | CAS7440-30-4 |
How to Locate Thulium on Periodic Table
Periodic table is arranged by atomic number, number of protons in the nucleus which is same as number of electrons. The atomic number increases from left to right. Periodic table starts at top left ( Atomic number 1) and ends at bottom right (atomic number 118). Therefore you can directly look for atomic number 69 to find Thulium on periodic table.
Another way to read periodic table and locate an element is by using group number (column) and period number (row). To locate Thulium on periodic table look for cross section of group - and period 6 in the modern periodic table.
Thulium History
The element Thulium was discovered by T. Cleve in year 1879 in Sweden. Thulium was first isolated by T. Cleve in 1879. Thulium derived its name from Thule, the ancient name for Scandinavia.
Cleve split Marignac's erbia into erbia proper and two new elements, thulium and holmium.
Thulium Presence: Abundance in Nature and Around Us
The table below shows the abundance of Thulium in Universe, Sun, Meteorites, Earth's Crust, Oceans and Human Body.
ppb by weight (1ppb =10^-7 %) | ppb by atoms (1ppb =10^-7 %) | |
---|---|---|
Abundance in Universe | 0.1 | 0.001 |
Abundance in Sun | 0.2 | 0.001 |
Abundance in Meteorites | 30 | 3 |
Abundance in Earth's Crust | 450 | 50 |
Abundance in Oceans | 0.0002 | 0.000007 |
Abundance in Humans | - | - |
Crystal Structure of Thulium
The solid state structure of Thulium is Simple Hexagonal.
The Crystal structure can be described in terms of its unit Cell. The unit Cells repeats itself in three dimensional space to form the structure.
Unit Cell Parameters
The unit cell is represented in terms of its lattice parameters, which are the lengths of the cell edges Lattice Constants (a, b and c)
a | b | c |
---|---|---|
353.75 pm | 353.75 pm | 555.46 pm |
and the angles between them Lattice Angles (alpha, beta and gamma).
alpha | beta | gamma |
---|---|---|
π/2 | π/2 | 2 π/3 |
The positions of the atoms inside the unit cell are described by the set of atomic positions ( xi, yi, zi) measured from a reference lattice point.
The symmetry properties of the crystal are described by the concept of space groups. All possible symmetric arrangements of particles in three-dimensional space are described by the 230 space groups (219 distinct types, or 230 if chiral copies are considered distinct.
Space Group Name | P63/mmc | ![]() |
Oxidation States | Space Group Number | 194 |
Crystal Structure | Simple Hexagonal |
Thulium Atomic and Orbital Properties
Thulium atoms have 69 electrons and the electronic shell structure is [2, 8, 18, 31, 8, 2] with Atomic Term Symbol (Quantum Numbers) 2F7/2.
Atomic Number | 69 |
Number of Electrons (with no charge) | 69 |
Number of Protons | 69 |
Mass Number | 169 |
Number of Neutrons | 100 |
Shell structure (Electrons per energy level) | 2, 8, 18, 31, 8, 2 |
Electron Configuration | [Xe] 4f13 6s2 |
Valence Electrons | 4f13 6s2 |
Valence (Valency) | 3 |
Main Oxidation States | 3 |
Oxidation States | 0, 1, 2, 3 |
Atomic Term Symbol (Quantum Numbers) | 2F7/2 |
Bohr Atomic Model of Thulium - Electrons per energy level

n | s | p | d | f |
---|
Ground State Electronic Configuration of Thulium - neutral Thulium atom
Abbreviated electronic configuration of Thulium
The ground state abbreviated electronic configuration of Neutral Thulium atom is [Xe] 4f13 6s2. The portion of Thulium configuration that is equivalent to the noble gas of the preceding period, is abbreviated as [Xe]. For atoms with many electrons, this notation can become lengthy and so an abbreviated notation is used. This is important as it is the Valence electrons 4f13 6s2, electrons in the outermost shell that determine the chemical properties of the element.
Unabbreviated electronic configuration of neutral Thulium
Complete ground state electronic configuration for the Thulium atom, Unabbreviated electronic configuration
1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6 4f13 6s2
Electrons are filled in atomic orbitals as per the order determined by the Aufbau principle, Pauli Exclusion Principle and Hund’s Rule.

Atomic Structure of Thulium
Thulium atomic radius is 222 pm, while it's covalent radius is - .
Atomic Radius Calculated | 222 pm (2.22 Å) |
Atomic Radius Empirical | 175 pm (1.75 Å) |
Atomic Volume | 19.13 cm3/mol |
Covalent Radius | - |
Van der Waals Radius | - |
Neutron Cross Section | 105 |
Neutron Mass Absorption | 0.025 |
Atomic Spectrum of Thulium
Thulium Chemical Properties: Thulium Ionization Energies and electron affinity
The electron affinity of Thulium is 50 kJ/mol.
Valence | 3 |
Electronegativity | 1.25 |
ElectronAffinity | 50 kJ/mol |
Ionization Energy of Thulium
Refer to table below for Ionization energies of Thulium
Ionization energy number | Enthalpy - kJ/mol |
---|---|
1st | 596.7 |
2nd | 1160 |
3rd | 2285 |
4th | 4120 |
Thulium Physical Properties
Refer to below table for Thulium Physical Properties
Density | 9.321 g/cm3(when liquid at m.p density is $8.56 g/cm3) |
Molar Volume | 19.13 cm3/mol |
Elastic Properties
Young Modulus | 74 |
Shear Modulus | 31 GPa |
Bulk Modulus | 45 GPa |
Poisson Ratio | 0.21 |
Hardness of Thulium - Tests to Measure of Hardness of Element
Mohs Hardness | - |
Vickers Hardness | 520 MPa |
Brinell Hardness | 471 MPa |
Thulium Electrical Properties
Thulium is Conductor of electricity. Refer to table below for the Electrical properties ofThulium
Electrical Conductivity | 1400000 S/m |
Resistivity | 7e-7 m Ω |
Superconducting Point | - |
Thulium Heat and Conduction Properties
Thermal Conductivity | 17 W/(m K) |
Thermal Expansion | 0.0000133 /K |
Thulium Magnetic Properties
Magnetic Type | Paramagnetic |
Curie Point | 25 K |
Mass Magnetic Susceptibility | 0.00000199 m3/kg |
Molar Magnetic Susceptibility | 3.36179e-7 m3/mol |
Volume Magnetic Susceptibility | 0.0185488 |
Optical Properties of Thulium
Refractive Index | - |
Acoustic Properties of Thulium
Speed of Sound | - |
Thulium Thermal Properties - Enthalpies and thermodynamics
Refer to table below for Thermal properties of Thulium
Melting Point | 1818 K (1544.85°C, 2812.73 °F) |
Boiling Point | 2223 K (1949.85°C, 3541.7299999999996 °F) |
Critical Temperature | - |
Superconducting Point | - |
Enthalpies of Thulium
Heat of Fusion | 16.8 kJ/mol |
Heat of Vaporization | 250 kJ/mol |
Heat of Combustion | - |
Thulium Isotopes - Nuclear Properties of Thulium
Thulium has 35 isotopes, with between 145 and 179 nucleons. Thulium has 1 stable naturally occuring isotopes.
Isotopes of Thulium - Naturally occurring stable Isotopes: 169Tm.
Isotope | Z | N | Isotope Mass | % Abundance | T half | Decay Mode |
---|---|---|---|---|---|---|
145Tm | 69 | 76 | 145 | Synthetic | ||
146Tm | 69 | 77 | 146 | Synthetic | ||
147Tm | 69 | 78 | 147 | Synthetic | ||
148Tm | 69 | 79 | 148 | Synthetic | ||
149Tm | 69 | 80 | 149 | Synthetic | ||
150Tm | 69 | 81 | 150 | Synthetic | ||
151Tm | 69 | 82 | 151 | Synthetic | ||
152Tm | 69 | 83 | 152 | Synthetic | ||
153Tm | 69 | 84 | 153 | Synthetic | ||
154Tm | 69 | 85 | 154 | Synthetic | ||
155Tm | 69 | 86 | 155 | Synthetic | ||
156Tm | 69 | 87 | 156 | Synthetic | ||
157Tm | 69 | 88 | 157 | Synthetic | ||
158Tm | 69 | 89 | 158 | Synthetic | ||
159Tm | 69 | 90 | 159 | Synthetic | ||
160Tm | 69 | 91 | 160 | Synthetic | ||
161Tm | 69 | 92 | 161 | Synthetic | ||
162Tm | 69 | 93 | 162 | Synthetic | ||
163Tm | 69 | 94 | 163 | Synthetic | ||
164Tm | 69 | 95 | 164 | Synthetic | ||
165Tm | 69 | 96 | 165 | Synthetic | ||
166Tm | 69 | 97 | 166 | Synthetic | ||
167Tm | 69 | 98 | 167 | Synthetic | ||
168Tm | 69 | 99 | 168 | Synthetic | ||
169Tm | 69 | 100 | 169 | 100% | Stable | |
170Tm | 69 | 101 | 170 | Synthetic | ||
171Tm | 69 | 102 | 171 | Synthetic | ||
172Tm | 69 | 103 | 172 | Synthetic | ||
173Tm | 69 | 104 | 173 | Synthetic | ||
174Tm | 69 | 105 | 174 | Synthetic | ||
175Tm | 69 | 106 | 175 | Synthetic | ||
176Tm | 69 | 107 | 176 | Synthetic | ||
177Tm | 69 | 108 | 177 | Synthetic | ||
178Tm | 69 | 109 | 178 | Synthetic | ||
179Tm | 69 | 110 | 179 | Synthetic |
Regulatory and Health - Health and Safety Parameters and Guidelines
Database Search
List of unique identifiers to search the element in various chemical registry databases
Database | Identifier number |
---|---|
CAS Number - Chemical Abstracts Service (CAS) | CAS7440-30-4 |
RTECS Number | - |
CID Number | CID23961 |
Gmelin Number | - |
NSC Number | - |