Gadolinium · element 64
A metal that turns magnetic in a cold room, catches neutrons better than anything, and lights up MRI scans
Key facts
Gadolinium sits at the exact centre of the lanthanide series, and its atoms carry seven unpaired electrons, the most of any element. That gives it some of the strongest magnetic behaviour in the periodic table. Cool a lump of gadolinium to around 20 °C and it becomes ferromagnetic, sticking to a fridge magnet like iron. No other element switches its magnetism so close to room temperature.
Those same electrons make gadolinium ions ideal for medical imaging. Injected in a safe chemical wrapper, they alter how nearby water molecules respond to a magnetic field and make tissues stand out sharply in MRI scans. And one of its isotopes absorbs neutrons more greedily than any other stable nucleus known, which has earned it a place in nuclear reactors.
Where it is found
Gadolinium is the most abundant of the heavier lanthanides but still occurs only in combination with the other rare earths. The main sources are the minerals monazite and bastnäsite, mined in China, the United States, Australia and elsewhere.
The mineral gadolinite, from which the element takes its name, actually contains little gadolinium. It was named in honour of Johan Gadolin, the Finnish chemist who first analysed the rare earth minerals of Ytterby in the 1790s, and the element was named after the mineral rather than directly after the man.
How it was discovered
The Swiss chemist Jean Charles Galissard de Marignac was a meticulous worker who spent years measuring atomic weights and picking apart the rare earths. In 1880 he examined the spectrum of an oxide obtained from samarskite and found lines belonging to an unknown element. He called the oxide gadolinia.
Six years later Paul-Émile Lecoq de Boisbaudran in Paris isolated the same oxide in pure form and, with Marignac's agreement, gave the element its name.
What we use it for
The use most people meet is in hospital. Gadolinium based contrast agents are injected before certain MRI scans. The gadolinium ion is bound tightly inside a large organic molecule, called a chelate, so it can pass safely through the body and be filtered out by the kidneys. While it circulates, it brightens blood vessels, inflamed tissue and tumours on the scan.
In nuclear engineering gadolinium-157 has the largest thermal neutron capture cross-section of any stable isotope. Gadolinium nitrate solution is used as an emergency shutdown poison in some reactors, and gadolinium oxide is mixed into fuel pellets to smooth out power over the life of the fuel.
Gadolinium compounds appear in electronics too. Gadolinium oxysulfide is a phosphor in X-ray detectors and screens, converting X-rays into visible light. Small amounts of gadolinium improve the workability and high temperature resistance of iron and chromium alloys.
Reading the numbers
Gadolinium melts at about 1312 °C and boils near 3000 °C, both higher than europium on its left, because gadolinium contributes three electrons to its metallic bonding rather than two. Its density of 7.9 grams per cubic centimetre is almost exactly that of iron.
The configuration [Xe] 4f7 5d1 6s2 breaks the simple pattern of filling the 4f shell one electron at a time. With seven electrons the 4f shell is exactly half full, and that arrangement is so stable that the eighth electron goes into a 5d orbital instead. Those seven unpaired electrons are what make gadolinium so strongly paramagnetic, and the +3 ion keeps all of them. Its first ionisation energy of about 593 kJ/mol is a little higher than its neighbours, another sign of that stable half filled shell. Position 64 puts it at the midpoint of the fifteen lanthanides, where the series turns from the lighter to the heavier rare earths.
Safety and the environment
Free gadolinium ions are toxic because they are similar in size to calcium ions and interfere with processes that depend on calcium. This is why medical contrast agents wrap the metal in a chelate. Even so, patients with severely reduced kidney function have suffered a serious skin and organ condition after some older agents, and modern practice screens for kidney problems before injection. Tiny amounts of gadolinium have been found to remain in the body after scans, and research into the significance of this continues.
Because contrast agents leave the body in urine, gadolinium is now detectable at trace levels in rivers and tap water downstream of hospitals in many cities. The concentrations are far below any known harmful level, but the trend is a reminder that medical chemistry can end up in the environment.
Did you know?
- Gadolinium becomes ferromagnetic below about 20 °C, so it will stick to a magnet on a cold day but not on a warm one.
- Gadolinium-157 has the highest thermal neutron capture cross-section of any known stable isotope, which is why it is used to shut reactors down.
- Gadolinium atoms have seven unpaired electrons, more than any other element, giving them exceptionally strong magnetic moments.
- Millions of MRI scans each year use gadolinium contrast agents, and traces of the metal from those injections can now be measured in city rivers.
- The element is named after the mineral gadolinite, which honours Johan Gadolin, though the mineral itself contains very little gadolinium.
- Gadolinium shows an unusually large magnetocaloric effect, heating up when magnetised and cooling when demagnetised, and has been used in experimental magnetic refrigerators.
More in the lanthanides
The nearest neighbours of gadolinium in the family, by atomic number.
See all 15 lanthanides on one page, or browse all 118 elements.
Frequently asked questions
Why is gadolinium used in MRI scans?
Gadolinium ions have seven unpaired electrons and are strongly magnetic, so they change how nearby water molecules respond to the scanner's magnetic field. This makes blood vessels, inflammation and tumours appear brighter. The gadolinium is bound inside a chelate molecule so it can be excreted safely.
Is gadolinium safe?
In its chelated form it is considered safe for most patients and has been used for decades. Free gadolinium ions are toxic, and people with severe kidney disease face a higher risk from some older agents, so doctors check kidney function first. Small residual traces in the body are being studied.
Is gadolinium magnetic?
Yes, strongly. Above about 20 °C it is paramagnetic, meaning it is attracted to a magnet but does not stay magnetised. Below that temperature it becomes ferromagnetic like iron, which is why it is described as having a Curie point near room temperature.
What is gadolinium used for besides medicine?
It absorbs neutrons extremely well, so it is used in nuclear reactor shutdown systems and in fuel. It also appears in X-ray detector phosphors, in garnets for optical and magnetic devices, and as an additive that improves iron and chromium alloys.
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Written by Anthony. Updated September 2026. Numerical data from Periodic-Table-JSON (CC BY-SA), cross-checked against the Gadolinium reference article. Spotted an error? Tell us.