Lutetium is a chemical element with atomic number 71 in the periodic table. This rare-earth metal occurs in a concentration of 0.8 to 1.7 ppm in Earth’s crust. As a member of the lanthanides family of periodic table elements, lutetium has three valence electrons. Its most significant practical applications include the dating of meteorites and nuclear medicine, as a part of cancer therapy protocols.
Chemical and Physical Properties of Lutetium
The symbol in the periodic table of elements: Lu
Atomic number: 71
Atomic weight (mass): 174.97 g.mol-1
Group number: Lanthanides
Color: Silvery-white rare earth metal
Physical state: Solid metal at room temperature
Half-life: From 43(5) milliseconds to 3.78 × 1010 years
Electronegativity according to Pauling: 1.2
Density: 9.7 g.cm-3 at 20°C
Melting point: 1663°C, 3025°F, 1936 K
Boiling point: 3402°C, 6156°F, 3675 K
Van der Waals radius: Unknown
Ionic radius: Unknown
Most characteristic isotope: 175Lu
Electronic shell: [Xe] 4f145d16s2
The energy of the first ionization: 522.7 kJ.mol-1
The energy of the second ionization: 1339 kJ.mol-1
Discovery date: Independently discovered in 1907 by Georges Urbain in Paris, France; (also independently discovered in the same period by Charles James in New Hampshire, United States; and Carl Auer von Welsbach, in Austria).
Lutetium is the chemical element with the periodic table symbol Lu. It has the atomic number 71, meaning that this element has 71 protons, 104 neutrons, and 71 electrons. Its atomic mass is 174.97 g.mol-1, while the electron configuration is expressed with the formula [Xe] 4f145d16s2.
Element 71 is a solid metal ductile and reaches its boiling point at 3402°C (6156°F, 3675 K), while its melting point is at 1663°C (3025°F, 1936 K). This member of the lanthanides family in the periodic table has an electronegativity of 1.2 according to Pauling, whereas the atomic radius according to van der Waals is still unknown.
Lutetium resembles calcium and magnesium in its reactivity. This rare silvery-white rare earth metal is soft and ductile and adopts the +3 oxidation state in its compounds. It tarnishes slowly when exposed to air. At 150°C, lutetium forms its oxides. Lutetium is relatively stable in air, it dissolves rapidly in acids, and it undergoes a slow chemical reaction when it comes into contact with H2O molecules.
How Was Lutetium Discovered?
The chemical element 71 was discovered independently by three scientists who were conducting their chemical trials in different parts of the world, at almost the same time. The mineral gadolinite that had been obtained from a mine near Ytterby, Sweden, turned out to be rich with various rare earth elements. That’s why many scientists were interested in the chemical analysis of the same mineral sample.
In 1843, the Swedish chemist Carl Gustaf Mosander succeeded in isolating yttria, erbia, and terbia from the gadolinite sample. The similarities among these three substances stirred up curiosity amongst the scientists even more. So, by 1878, the Swiss chemist Jean Charles Galissard de Marignac became the first scientist who had managed to observe two different components in the erbia sample – one was labeled ytterbia, while the other substance kept the name erbia.
As gadolinite proved to be a rich source of new rare earth elements that could be further separated into new chemicals, de Marignac held the belief that ytterbia is also a compound that contains a new element – the ytterbium.
Georges Urbain’s Discovery
Following the advancements of his colleagues, the French chemist Georges Urbain (1872 – 1938) also attempted individual experiments on an ytterbium sample. As the other chemists were unsuccessful in providing scientific evidence of the chemical properties of the new element, Urbain believed that their efforts were misdirected.
Namely, this French chemist was convinced that even the new element was a compound that can be further separated into other elements. This could also explain why it was difficult for many scientists to determine any of the ytterbium properties as fixed.
So, Georges Urbain decided to apply the fractional crystallization method on a ytterbium nitrate sample obtained from a nitric acid solution. He managed to produce two rare earth oxides. One of the oxides kept the name of ytterbium (neoytterbium), while the other was named ‘lutecium’ at first. Later, the name of the new element 71 was altered into lutetium.
Charles James’ Revolutionary Method
In 1906, an American chemist of British origin, Charles James (1880 – 1928), also managed to isolate the lutetium from a ytterbium sample, except that he went a step further by revolutionizing the bromate fractional crystallization process. This process proved to be quite valuable for the further discovery and isolation of new rare earth metals.
Until the 1940s, when the ion exchange techniques were discovered, James’ bromate fractional crystallization process eased the work of scientists who were going through the difficult process of distinguishing the rare earth elements from mineral samples.
The Contribution of Carl Auer von Welsbach
Austrian scientist and inventor Baron Carl Auer von Welsbach (1858 – 1929) also had an interest in rare-earth elements. In 1907–08, Baron von Welsbach also succeeded in separating the lutetium element from the ytterbium. He chose the names albebaranium and cassiopeium for the two new substances.
How Did Lutetium Get Its Name?
Since the French chemist Georges Urbain was the first scientist who succeeded in separating lutetium from the ytterbium as an individual substance, he was given the opportunity to name the new chemical element.
Georges Urbain chose the Latin term ‘lutetia’ to name his newly discovered element, which is the ancient name for Paris – the capital city of Urbain’s home country.
Where Can You Find Lutetium?
Lutetium is a rare earth metal that can be found in nature in very small quantities as a part of all mineral formations that contain yttrium. Most commonly, it occurs in the orthophosphate minerals xenotime and monazite, as well as in the fluoride carbonate mineral ore called bastnaesite.
Apart from the lutetium, the other lanthanides that can be extracted from these mineral formations are cerium, lanthanum, neodymium, and praseodymium. The chemicals thorium and yttrium can also be isolated from the monazite mineral. However, due to the high radioactive properties of thorium and the byproducts of its decay, the process of isolating the chemicals is quite difficult and dangerous.
The pure, elemental form of the lutetium metal is produced by a reduction of anhydrous LuCl3 or LuF3 by an alkali or alkaline earth metal:
2LuF3 + 3Ca → 2Lu + 3CaF2
For commercial uses, this chemical substance is mainly obtained through the ion exchange process from monazite sand ((Ce, La, Th, Nd, Y)PO4).
Lutetium in Everyday Life
Although it’s difficult to be isolated and produced, lutetium has several significant applications:
- Lutetium oxides, i.e. stable lutetium nuclides that emit pure beta radiation after thermal neutron activation are used in the manufacturing of catalysts for cracking hydrocarbons in the petrochemical industry, as well as in alkylation, hydrogenation, and polymerization processes;
- The radioactive lutetium-177 isotope has a highly significant application in radiology and cancer therapy. More specifically, lutetium radioisotopes are applied in the therapy of prostate cancer patients. The lutetium PSMA therapy slows down the growth of tumorous cells, reduces the size of the tumors, and reduces the pain of the patients;
- Lutetium ions were often used to dope gadolinium gallium garnet in the production of magnetic bubble computer memory. Nowadays, this type of memory storage is replaced by the more sophisticated computer hard drives;
- Element 71 and its radioactive isotopes are used in detectors of positron emission tomography to monitor the cellular activity of the body;
- Lutetium also has a practical application in the dating of meteorites.
How Dangerous Is Lutetium?
While the insoluble salts are non-toxic, the pure metal form of lutetium is considered to have a mild toxic effect upon ingestion. However, when combined with other chemical elements, lutetium compounds might be extremely toxic or hazardous. Some of these mixtures tend to pose a fire hazard or result in volatile explosions because of the chemical properties of the compounding chemicals.
Environmental Effects of Lutetium
While the pure elemental form of lutetium doesn’t pose any threat to the environment, its metal dust may trigger specific volatile reactions that can result in fire or an explosion.
Isotopes of Lutetium
Lutetium has 35 forms with an atomic mass ranging from 150Lu to 184Lu. The form of lutetium that can be found in the Earth’s crust is made up of two isotopes – the stable 175Lu isotope (with 97.41% natural abundance) and the 176Lu radioisotope (with 2.59% natural abundance).
With a half-life of 3.78 × 1010 years, the lutetium-176 radioisotope is also the longest living form of this chemical element. The heavier isotopes of lutetium decay through beta decay, producing hafnium isotopes.
|Z||N||Isotopic mass (Da)
[n 2][n 3]
[n 4][n 5]
[n 8][n 5]
|Natural abundance (mole fraction)|
|Excitation energy[n 5]||Normal proportion||Range of variation|
|150Lu||71||79||149.97323(54)#||43(5) ms||p (80%)||149Yb||(2+)|
|151Lu||71||80||150.96757682||80.6(5) ms||p (63.4%)||150Yb||(11/2−)|
|152Lu||71||81||151.96412(21)#||650(70) ms||β+ (85%)||152Yb||(5−, 6−)|
|β+, p (15%)||151Tm|
|153Lu||71||82||152.95877(22)||0.9(2) s||α (70%)||149Tm||11/2−|
|155Lu||71||84||154.954316(22)||68.6(16) ms||α (76%)||151Tm||(11/2−)|
|156Lu||71||85||155.95303(8)||494(12) ms||α (95%)||152Tm||(2)−|
|157Lu||71||86||156.950098(20)||6.8(18) s||β+||157Yb||(1/2+, 3/2+)|
|158Lu||71||87||157.949313(16)||10.6(3) s||β+ (99.09%)||158Yb||2−|
|159Lu||71||88||158.94663(4)||12.1(10) s||β+ (99.96%)||159Yb||1/2+#|
|175Lu||71||104||174.9407718(23)||Observationally Stable[n 9]||7/2+||0.9741(2)|
|176Lu[n 10][n 11]||71||105||175.9426863(23)||38.5(7)×109 y||β−||176Hf||7−||0.0259(2)|
List of Lutetium Compounds
When lutetium is a part of a compound, it usually adopts the trivalent oxidation state (Lu3+). Most lutetium salts are colorless, which makes them difficult to register through the method of spectroscopy.
Some of the most common lutetium compounds include:
- Lutetium (177Lu) chloride
- Lutetium (177Lu) oxodotreotide
- Lutetium aluminium garnet
- Lutetium phthalocyanine
- Lutetium tantalate
- Lutetium–yttrium oxyorthosilicate
- Lutetium(III) bromide
- Lutetium(III) chloride
- Lutetium(III) fluoride
- Lutetium(III) hydroxide
- Lutetium(III) oxide
- Motexafin lutetium
5 Interesting Facts and Explanations
- Lutetium is the last natural rare earth element and member of the lanthanide family that was discovered. There are two main reasons for this: first, it’s a scientific fact that the abundance of an element decreases as its atomic number increases; second, elements with odd atomic numbers (such as lutetium) are less abundant than elements with even atomic numbers (like ytterbium).
- The estimated oceanic abundance of lutetium amounts to 1.5×10-7 milligrams per liter, while its occurrence in the Earth’s core is calculated to be 8×10-1 milligrams per kilogram.
- Lutetium does not form colorful compounds. As it’s spectroscopically transparent, it’s difficult to trace it in mineral ores.
- This rare-earth element is characterized as the densest and hardest lanthanide out of all the members of this family of elements.
- Despite being labeled as ‘rare’, lutetium is an element that can be found in nature more frequently than silver or gold.