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Lutetium is a rare earth metal in the lanthanide series of the periodic table. It is the last member of the lanthanide series and is regarded as a very rare and expensive element. It is denoted as Lu and bears atomic number 71. It is a metal that resists corrosion in dry air. This metal is silvery-white, malleable, soft, and ductile. It can be sourced from nearly all minerals that contain the similar element, yttrium.
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What is Lutetium?
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Lutetium is a chemical element with atomic number 71. Lutetium is basically denoted as Lu. It is a rare earth metal of the lanthanide series of the periodic table. It is regarded as the densest and the highest melting rare earth element. It is the last member of the lanthanide series.
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When in its purest form lutetium is a silvery white metal and it is stable in air. Except hydrofluoric acid (HF) this metal is easily dissolvable in all kinds of dilute acids. When it comes in contact with hydrofluoric acid (HF) it forms a protective layer of LuF3 on the surface of the metal and prevents the metal from further dissolution.
Fig. Lutetium in its purest form
| PARTICULARS | DETAILS |
|---|---|
| Periodic Table Classification | Group 3 Period 6 |
| State at 20C | Solid |
| Colour | Silvery white |
| Atomic number | 71 |
| Electron Configuration | [Xe] 4f14 5d1 6s2 |
| Electron Number | 71 |
| Proton Number | 71 |
| Electron Shell | 2, 8, 18, 32, 9, 2 |
| Density | 9.84 g.cm-3 at 20°C |
| Atomic Mass | 174.97 g.mol -1 |
| Electronegativity according to Pauling | 1.27 |
| Discovered by | George Urbain in 1907 |
Discovery of Lutetium
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In 1907 Lutetium was discovered independently by Georges Urbain and Carl Auer von Welsbach and Charles James. It was found to be impure in ytterbium. Ytterbium was separated into two components neo ytterbia and lutecia by Georges Urbain.
Neoytterbia later was called ytterbium and lutecia as lutetium. Carl Auer von Welsbach at the same time carried out the research independently, and he called the new elements aldebaranium and cassiopeia. In 1907 the names were finalized as lutetium by George Urbain. In 1953 its pure metal form was manufactured.
Fig. Lutetium Atomic Structure
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Occurrence of Lutetium
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Lutetium is not found freely in nature and is present along with several rare minerals. It is not an abundant element and commonly is found as constituent of yttrium minerals. Lutetium is relatively rare and its extraction is also very challenging. It is one of the most expensive rare earth metals and its price is around one-fourth of the price of gold. Lutetium is found in countries like China, Brazil, USA, India, Sri Lanka and Australia.
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Physical Properties of Lutetium
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- Lutetium is the hardest metal in the lanthanide series and it is silvery white in colour.
- It is unstable in air and can burn at 150oC to form lutetium oxide Lutetium.
- It has the highest melting point among the lanthanides, 1652oC and boiling point of 3402oC.
- The density of lutetium is around 9.841 g/cm3 at room temperature and is also the highest among the other members of lanthanide series.
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Chemical Properties of Lutetium
- Lutetium gets oxidized in moist air.
- It gets easily dissolved in weak acids except hydrofluoric acid (HF)
- Lutetium comes in contact with hydrofluoric acid (HF) and forms a protective layer of LuF3 on the surface of the metal and prevents the metal from further dissolution.
- It reacts with four halogens, except fluoride to form trihalides.
- Most salts of lutetium are soluble in water and when the solution is dried. they tend to produce white crystals.
- Lutetium mostly exists in the oxidation state of +3.
- Lutetium carbonate, lutetium oxides are insoluble while Lutetium sulfate, lutetium nitrate and lutetium acetate are water soluble.
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Isotopes of Lutetium
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There are about 32 synthetic radioactive isotopes of lutetium (lutetium-150 to lutetium-184), and their atomic masses ranging from 149.97 to 183.96. Amongst all of them the most stable radioactive isotope is lutetium-174 and has a half-life of 1.37 years.
Other than that lutetium has two isotopes: lutetium-175 and lutetium-176. The isotope lutetium-176 has an abundance of 2.5% and is a radioactive isotope. It has a half-life of 38 billion years.
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Lutetium Uses
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Lutetium is a rare and expensive metal, plus it has very low abundance and hence it has few commercial uses. So, some of its uses are described below:
- It is used as a catalyst in the petroleum industry.
- Lutetium is used to make various useful alloys. For instance, lutetium aluminium garnet is used to make lenses.
- Lutetium-176 is used in dating of rocks and meteorites.
- Lutetium tantalite is used as an ideal host for X-ray phosphor as it has tremendously high density and is very stable.
- Lutetium-177 is a medically useful isotope and is used for treatment of bone palliation and tumour therapy, especially endocrine tumours.
- Lutetium is used to carry out polymerization, alkylation and hydrogenation reactions.
- Lutetium aluminium is used to make phosphor in LED light bulbs.
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Health Effects of Lutetium
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- Lutetium is considered as one of the most toxic metals. But in its purest form it is regarded to be non-toxic.
- Its salts, especially water-soluble compounds, are considered most toxic.
- The lutetium compounds are specially suggested to store in airtight glass containers away from the moisture and direct contact of air.
- Due to its toxicity, it causes skin diseases when a person comes in contact with it.
- It may lead to substantial explosions when heated.
- Inhalation of this compound is basically very dangerous and can result in fatal conditions.
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Things to Remember
- Lutetium is a rare earth metal of the lanthanide series of the periodic table. It is regarded as the densest and the highest melting rare earth element.
- Some amount of lutetium is present in the human body in bones and in even more restricted amounts in liver and kidneys.
- The most stable radioactive isotope is lutetium-174 and has a half-life of 1.37 years.
- The salts of lutetium, especially water-soluble compounds, are most toxic.
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Sample Questions
Ques. What is the half-life of the element lutetium? (2 Marks)
Ans. Lutetium-176 is a relatively abundant (2.5%) radioactive isotope with a half-life of about 38 billion years, used to determine the age of minerals and meteorites.
Ques. What is the electronic configuration of Lu2+? (2 Marks)
Ans. Lu2+ = 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6 4f14 5d1
Or [Xe]54 2f14 3d3
Ques. Which form of lutetium is considered as most toxic? (2 Marks)
Ans. Lutetium in its purest form is a silvery white metal. Lutetium itself is regarded to have a low degree of toxicity and some amount of lutetium is also considered to be found in bones, and even lesser in kidneys and liver. Nonetheless the salts of Lutetium, especially water-soluble compounds are considered most toxic.
Ques. Which is the most stable radioactive isotope of lutetium? (2 Marks)
Ans. They range in mass from 150 to 184; the least stable isotope (lutetium-150) has a half-life of 45 milliseconds, and the most stable isotope is lutetium-176.
Ques. Lutetium gets tarnished in moist air. Explain the statement. (2 Marks)
Ans. Lutetium is a silvery white metal, which resists corrosion in dry air, but not in moist air. It goes into oxidation when it comes in contact with moist air. The water droplets present in the moist air happen to tarnish the earth metal completely.
Ques. Write down some of the uses of astatine. (2 Marks)
Ans.
- Lutetium gets oxidized in moist air.
- It gets easily dissolved in weak acids except hydrofluoric acid (HF)
- Lutetium comes in contact with hydrofluoric acid (HF) and forms a protective layer of LuF3on the surface of the metal and prevents the metal from further dissolution.
- It reacts with four halogens, except fluoride to form trihalides.
Ques. Lutetium belongs to which group? (3 Marks)
Ans. The element with atomic number 71 is known as Lutetium. Its symbol is Lu. It belongs to the Lanthanide series of the f-block of the periodic table which consists of elements from atomic number 57 to 71.
It is not found in a pure state in nature but is obtained from its chloride through a reduction process by alkaline metals. Lutetium 177 is a radioactive isotope of Lutetium. Lutetium is a rare earth metal. Lutetium is the last element of the lanthanide series and it belongs to group 3 elements, because they have a single valence electron in the 5d shell.
Ques. Why is lutetium excluded from the lanthanide group? (2 Marks)
Ans. Lutetium is the last element of the lanthanide series, and it is counted as one of the rare earth metals. Still there are some references that exclude lutetium from the lanthanide group because it has a single valence electron in the 5d shell.
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