Gadolinium
Gadolinium is a chemical element with symbol Gd and atomic number 64. It is a silvery-white, malleable and ductile rare-earth metal. It is found in nature only in combined (salt) form.
Identity
- Atomic mass
- 157.253 u
- Category
- Lanthanides
- Group
- 3
- Period
- 6
- Block
- f
- Oxidation States
- +3
- Phase (25 °C)
- Solid
- Appearance
- silvery white
Electronic Structure
- Electron configuration
- 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f7 5d1
- Short configuration
- [Xe] 4f7 5d1 6s2
- Electrons per shell
- 2, 8, 18, 25, 9, 2
- Electronegativity (Pauling)
- 1.20
- Electron affinity
- 13.2 kJ/mol
- 1st ionization energy
- 593 kJ/mol
- Ionization energies
- 593 · 1170 · 1990 · 4250 kJ/mol
Physical properties
- Melting point
- 1311.8 °C (1585 K)
- Boiling point
- 2999.8 °C (3273 K)
- Density
- 7.9 g/cm³
- Molar heat capacity
- 37.0 J/(mol·K)
Chemical behavior of gadolinium
Gadolinium has eight outer electrons ([Xe] 4f⁷ 5d¹ 6s²) and almost always acts as +3, with low electronegativity (1.20). Its half-filled 4f shell gives it the highest magnetic moment among the elements at room temperature and an exceptional capacity to capture neutrons. It is malleable, oxidizes slowly in dry air and rapidly in moist air.
Reactivity
4 Gd + 3 O₂ → 2 Gd₂O₃
In dry air it tarnishes slowly; in moist air it becomes covered with a white oxide that flakes off. When heated, it burns to the oxide.
2 Gd + 6 H₂O → 2 Gd(OH)₃ + 3 H₂
It reacts slowly when cold and vigorously when hot, releasing hydrogen. The medical chelates keep the free ion from touching the body's water.
2 Gd + 6 HCl → 2 GdCl₃ + 3 H₂
It dissolves in dilute acids giving colorless gadolinium(III) salts. The chloride is the raw material for contrast chelates.
Gd + 3 Cl₂ → 2 GdCl₃
With halogens it gives trihalides on heating. With hydrogen it forms non-stoichiometric hydrides that absorb and release H₂.
Notable compounds
| Compound | Formula | Use or importance |
|---|---|---|
| Gadolinium oxide | Gd₂O₃ | Phosphors and technical ceramics |
| Gd-DOTA chelate | GdC₁₆H₂₅N₄O₈ | Magnetic resonance contrast |
| Gd-Y garnet | Gd₃Ga₅O₁₂ | Microwaves and magnetic memories |
| Gadolinium chloride | GdCl₃ | Contrast agents and magnetic materials |
| Gadolinium sulfate | Gd₂(SO₄)₃ | Experimental magnetic refrigeration |
Electron shell distribution
View in the atom builderIsotopes
Natural gadolinium mixes six stable isotopes plus one nearly stable: 154Gd (~2.2%), 155Gd (~14.8%), 156Gd (~20.5%), 157Gd (~15.7%), 158Gd (~24.8%) and 160Gd (~21.9%), all with 64 protons. 157Gd has the greatest thermal-neutron capture cross section known. 152Gd is a primordial radionuclide with a very long half-life.
Occurrence and production
It appears at about 6 ppm in bastnasite and monazite alongside europium and terbium. The main deposits are in China, the United States and Australia. It is obtained by acid dissolution, solvent extraction and ion exchange, and the metal by electrolysis of molten fluorides or reduction with calcium.
History and origin of the name
Jean Charles Galissard de Marignac detected it in 1880 in samarskite and Lecoq de Boisbaudran confirmed the new oxide in 1886. They named it gadolinium after Johan Gadolin, the Finnish chemist who studied ytterbite. For a century it was a magnetic curiosity until resonance contrast took it into every hospital.
Applications and relevance of gadolinium
Uses of the element
As a metal it enters magnetocaloric alloys that heat and cool with magnets, garnets for microwaves and control rods that absorb neutrons in reactors. Its magnetism cools without compressors in magnetic refrigeration.
Uses of its compounds
Gadolinium chelates are the standard resonance contrast: they light up tumors, blood vessels and inflammation. The oxide dopes green phosphors and gadolinium–yttrium garnet guides microwaves in radars and satellites.
Health, safety and environment
Biological role
The free ion is toxic and is retained in liver and bone, but in medicine it travels encapsulated in very stable macrocyclic chelates that are excreted in urine. In severe renal failure it requires caution because of nephrogenic fibrosis.
Safety
Metallic powder can burn and requires an inert atmosphere in industry. Contrast agents are administered only by prescription, at the minimum dose and with renal monitoring; allergic reactions are rare.
Environment
It shares the mining footprint of the rare earths. The chelates excreted in urine reach rivers and are hard to remove, so hospital retention is being researched. Its nuclear use avoids CO₂ emissions.
Frequently asked questions about Gadolinium
Why is gadolinium used in magnetic resonance scans?
Gadolinium is paramagnetic: when placed in the magnetic field of a resonance scanner, it alters the behavior of nearby protons and increases the signal of certain tissues. That is why gadolinium-based contrast agents allow better visualization of blood vessels, tumors, inflammation and areas with an altered blood-brain barrier. The element is not administered as a free metal, but bound to chelating molecules that control its behavior in the body.
Is gadolinium retained in the body after a resonance scan?
Some retention of gadolinium in tissues can occur, especially after repeated exposures and depending on the type of contrast agent used. Macrocyclic agents are usually more stable than some linear agents, which can release more free gadolinium. In clinical practice, administration takes place only when the expected diagnostic benefit justifies the procedure, respecting the minimum necessary doses and renal contraindications.
What is the difference between gadolinium and iodinated contrast?
Gadolinium contrast is used mainly in magnetic resonance imaging, while iodinated contrast is used above all in X-rays, CT scans and vascular studies with X-rays. They act differently: gadolinium modifies the magnetic signal of tissues, and iodine absorbs X radiation. In addition, their risks and contraindications are not identical, so the choice depends on the type of scan, the area studied and the patient's kidney function.
What other uses does gadolinium have besides medicine?
Besides resonance contrast, gadolinium is used in phosphors, gadolinium–yttrium garnets for microwave technology and alloys that improve high-temperature and oxidation resistance. It is also used in neutron control in nuclear reactors and has been studied in magnetic and superconducting materials. This diversity stems from its magnetic properties, its ability to capture neutrons and its behavior in ceramic and crystalline compounds.
Is gadolinium contrast safe?
Gadolinium contrasts are considered safe for most patients when they are used according to medical indications and at the right dose. However, they can increase the risk of nephrogenic systemic fibrosis in people with severe renal failure or acute kidney injury. For this reason, the medical team evaluates kidney function before administering them. Allergic reactions may also occur, although they are uncommon.
What is gadolinium used for in nuclear reactors?
Gadolinium has an exceptional capacity to capture thermal neutrons, greater than that of other known elements. This property allows it to be used in nuclear reactor control materials, where it helps regulate the chain reaction by absorbing neutrons. It is also used in the form of compounds or alloys in specialized nuclear applications. Its effectiveness as a neutron absorber makes it a strategic material for reactor safety and control.
Where does gadolinium come from?
Gadolinium is extracted from rare-earth minerals such as bastnasite and monazite, together with other lanthanides. After processing the ore, it is separated by solvent extraction and ion exchange, techniques capable of distinguishing chemically very similar elements. It can then be obtained as an oxide, salt or metal. Its relative availability and its magnetic and neutronic properties explain its importance in medicine, energy and technology.
Main sources consulted: PubChem, Royal Society of Chemistry, NIST, IUPAC. Last revision: November 2026.