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Exploring the Unique Chemical Properties of Thulium

Thulium: A Rare-Earth Element with Fascinating Chemical Properties

Thulium is a rare-earth element that is named after the mythical Northern land of Thule. It was first discovered by Swedish chemist Per Teodor Cleve in 1879 while he was analyzing the rare-earth mineral erbium oxide.

Thulium is a silvery lustrous metal with exceptional chemical properties that add to its uniqueness. In this article, we will discuss the chemical properties of thulium, its periodic table information, and its industrial uses.

Physical Properties

Thulium has a silvery luster, which adds to its aesthetic value. It is both malleable and ductile, meaning that it can be shaped or pulled into wires without breaking or losing its metallic properties.

Thulium has numerous radioisotopes that are of great significance in radiography and nuclear medicine. These isotopes are used to study various biological and chemical processes within the human body, and also in industrial applications.

Chemical Properties

Thulium’s electronic configuration enables it to have multiple oxidation states ranging from +2 to +4. The abundance of thulium in the earth’s crust is approximately 0.5 mg/kg, making it one of the rarest elements.

In its highest known oxidation state, +4, thulium forms yellow-brown salts that are soluble in water. In its +3 oxidation state, thulium forms white salts that are also soluble in water.


Thulium has 31 known isotopes; however, only one of them is stable. The most abundant isotope is the stable ^169Tm, which constitutes 100% of the naturally occurring thulium.

The rest of the isotopes are artificial, and many of them have been synthesized through nuclear reactions.

Electronic Shell

Thulium’s electronic configuration is [Xe] 4f^13 6s^2. This indicates that the outermost shell, or valence shell, has two electrons in the s orbital and thirteen electrons in the f orbitals.

The electronic distribution of thulium enables it to have unique chemical properties.

Ionization Energy

Ionization energy is the energy required to remove an electron from an atom or ion. Thulium has three ionization energies, namely the first, second, and third ionization energies.

The first ionization energy of thulium is 596.7 kJ/mol, the second is 1160 kJ/mol, and the third is 2285 kJ/mol. The large third ionization energy indicates that it is difficult to remove a third electron from thulium.


Allotropes are different forms or structures of the same element. Thulium has two allotropes: tetragonal and hexagonal.

The tetragonal allotrope has a close-packed structure with a distorted unit cell of four atoms. In contrast, the hexagonal allotrope is a high-temperature modification that has a hexagonal close-packed structure.

Periodic Table Information

Thulium is a lanthanide element, located in the sixth period and the f-block of the periodic table. Its atomic number is 69, indicating that it has 69 protons and 69 electrons.

Thulium has a Pauling electronegativity of 1.25, which makes it a relatively weak electronegative element compared to other elements. Thulium’s atomic density is 9.3 g/cm^3, which is higher than many other metals.

Industrial Uses

Due to its exceptional chemical properties, thulium has numerous applications in various industries. For instance, its stable isotope ^169Tm is used to detect defects, cracks, or damage in metal structures.

Thulium-doped fiber amplifiers are essential components of long-distance telecommunication. Thulium is also used in high-temperature superconductors, X-ray machines, and laser technology.


Thulium is a rare-earth element that is known for its unique chemical properties. Its electronic configuration enables it to have multiple oxidation states, and it has a multitude of radioisotopes that are useful in radiography and nuclear medicine.

Thulium also has industrial applications, such as in laser technology and telecommunications. This article discussed thulium’s chemical properties, its position in the periodic table, and its uses in various industries.

Thulium Chemical Classification and State

Thulium is a rare earth metal, which is a group of seventeen elements that have similar chemical and physical properties. All rare earth metals have electron configurations that end with a partially filled 4f shell.

Thulium is also a reactive metal, which means that it readily reacts with other elements to form new compounds. In fact, pure thulium is so reactive that it will ignite spontaneously when exposed to air.

This makes it challenging to handle and work with in its pure form. Thulium is a solid at room temperature, with a melting point of 1545°C and a boiling point of 1950°C.

Its density is approximately 9.32 g/cm^3, and it has a Mohs hardness of between 1.2 and 3.0. These physical properties are typical of most metals and contribute to thulium’s industrial applications.


Paramagnetism is the tendency of a material to become magnetized when exposed to an external magnetic field. Thulium exhibits paramagnetic behavior because it has unpaired electrons in its f orbitals.

When an external magnetic field is applied, these unpaired electrons align their spins, which creates a net magnetic moment that is parallel to the applied field. The strength of the induced magnetic moment is directly proportional to the strength of the applied magnetic field.

Thulium’s paramagnetic nature makes it a useful element in MRI (magnetic resonance imaging) machines. MRI utilizes the behavior of paramagnetic elements like thulium to produce high-resolution images of the human body.

In MRI, thulium ions are introduced into the patient’s body, and they align themselves with the magnetic field created by the MRI machine. Then, radio waves are applied to the thulium ions, which cause them to emit energy that is detected by the MRI machine.

The resulting image shows a 3D map of the patient’s body structure, allowing doctors to diagnose various health conditions.

Thulium Identification

Thulium is represented by the chemical symbol Tm, which is derived from its name. Its atomic number is 69, which implies that it has 69 protons and 69 electrons.

Thulium’s position in the periodic table indicates its electronic configuration, which is [Xe] 4f^13 6s^2. This electronic configuration is similar to other rare earth elements.

The rare earth elements are highly valued for their unique electronic configurations and their usefulness in various industrial applications. Thulium has a CAS number of 7440-30-4, which is assigned to all compounds that contain thulium.

The Chemical Abstracts Service (CAS) number is a unique identifier for chemical substances and is widely used in chemical databases. Thulium’s ChemSpider ID is 22398, which is a unique identifier in the ChemSpider database.

The ChemSpider database provides comprehensive information about chemical compounds, their properties, and their structures. Thulium’s ChemSpider ID can be used to obtain detailed information about its chemical compounds.

In summary, thulium is a rare earth metal that is represented by the chemical symbol Tm. It is a reactive metal that readily reacts with other elements to form new compounds. Thulium exhibits paramagnetic behavior, making it useful in MRI machines.

Its densities and melting/boiling points make it useful for industrial applications. Thulium has a CAS number of 7440-30-4 and a ChemSpider ID of 22398.

These identifiers make it possible to obtain detailed information about thulium’s chemical compounds. In conclusion, thulium is a rare earth metal with unique chemical and physical properties.

Its electronic configuration and paramagnetic nature make it useful in various fields, including radiography and MRI machines. Thulium’s high densities and melting/boiling points contribute to its industrial applications.

Its chemical classification and identification make it recognizable and useful for research and development. Studying the properties and applications of thulium can enhance our understanding of rare earth metals and their applications in different industries.


1. What is the electronic configuration of thulium?

Thulium’s electronic configuration is [Xe] 4f^13 6s^2.

2. What is thulium used for in MRI machines?

Thulium is used in MRI machines because of its paramagnetic behavior, allowing high-resolution images of the human body.

3. How does thulium react with other elements?

Thulium is a reactive metal that readily reacts with other elements to form new compounds.

4. What is the ChemSpider ID for thulium?

Thulium’s ChemSpider ID is 22398.

5. What is the melting point of thulium?

Thulium’s melting point is 1545°C.

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