Gadolinium
[Xe] 4f⁷ 5d¹ 6s² · 2 · 8 · 18 · 25 · 9 · 2
Apart from iron, cobalt, nickel and dysprosium, the only element ferromagnetic near room temperature: gadolinium's Curie point is 292 K, just under 19 °C. Gadolinium-157 has the largest thermal neutron capture cross-section of any nuclide.
3D model
Bohr model: nucleus and electron shells from the real configuration. Valence electrons are highlighted.
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Atomic properties
- Atomic number
- 64
- Atomic mass
- 157.25 а.е.м.
- Electron configuration
- [Xe] 4f⁷ 5d¹ 6s²
- Electrons per shell
- 2 · 8 · 18 · 25 · 9 · 2
- Block
- f-block
- Group
- no data
- Period
- 6
- Electronegativity (Pauling)
- 1.2
- Electronegativity (Allen)
- 1.11
- Atomic radius
- 237 pm
- Covalent radius
- 196 pm
- Van der Waals radius
- 237 pm
- Ionisation energy 1
- 593.4 kJ/mol
- Ionisation energy 2
- 1 170 kJ/mol
- Ionisation energy 3
- 1 990 kJ/mol
- Ionisation energy 4
- 4 250 kJ/mol
- Electron affinity
- 50 kJ/mol
- Common oxidation states
- +3
- Oxidation states
- +1, +2, +3
Physical properties
- State at 25 °C
- solid
- Density
- 7.9 g/cm³
- Melting point
- 1 585 K · 1 311.9 °C
- Boiling point
- 3 546 K · 3 272.9 °C
- Speed of sound
- 2 680 m/s
Thermal properties
- Heat of fusion
- 10.05 kJ/mol
- Heat of vaporisation
- 301.3 kJ/mol
- Specific heat capacity
- 0.236 J/(g·K)
- Thermal conductivity
- 10.6 W/(m·K)
Mechanical properties
- Young's modulus
- 54.8 GPa
- Shear modulus
- 21.8 GPa
- Bulk modulus
- 37.9 GPa
- Poisson ratio
- 0.26
- Mohs hardness
- no data
- Brinell hardness
- 570 MPa
Electrical and magnetic properties
- Electrical resistivity
- 1 310 nΩ·m
- Magnetic ordering
- ferromagnetic
- Curie point
- 292 K
- Néel point
- no data
- Superconducting point
- no data
Crystal structure
- Crystal structure
- hexagonal close-packed (hcp)
- Lattice constants
- a = 363.6 pm · c = 578.26 pm
Abundance
- In the crust
- 6.2 mg/kg
- In the ocean
- 7·10⁻⁷ mg/L
- In the universe
- 0.2 mg/kg
- In the human body
- no data
Isotopes
| Isotope | Abundance | Half-life | Decay mode |
|---|---|---|---|
| 152Gd | 0.2 % | 107 741.71 Gyr | α |
| 154Gd | 2.18 % | stable | — |
| 155Gd | 14.8 % | stable | — |
| 156Gd | 20.47 % | stable | — |
| 157Gd | 15.65 % | stable | — |
| 158Gd | 24.84 % | stable | — |
| 160Gd | 21.86 % | stable | — |
Gadolinium-157 captures thermal neutrons with a cross-section of 254 000 barns — larger than any other known nuclide.
Discovery
- Year of discovery
- 1880
- Discovered by
- Jean Charles Galissard de Marignac
- Where
- Switzerland
- Origin of the name
- after Johan Gadolin, who discovered yttrium
History
Marignac isolated the oxide in 1880 and Lecoq de Boisbaudran obtained the pure substance in 1886. It is named after Johan Gadolin, who discovered yttrium.
Where it occurs
6.2 mg/kg of the crust, travelling with the other heavy lanthanides in bastnäsite and monazite.
How it is produced
By solvent extraction, then metallothermic reduction of the fluoride with calcium.
Role in living things
No biological role. The free gadolinium ion is toxic, so medicine administers it only as a tightly bound chelate.
Safety
In patients with severe kidney failure, gadolinium contrast caused nephrogenic systemic fibrosis; once the link was established, its use was tightly restricted.
Uses
- MRI contrast agents: gadolinium complexes sharply brighten tissue signal
- Control rods and burnable poisons in nuclear reactors
- Magnetic refrigeration — gadolinium warms in a magnetic field and cools out of it
- Phosphors and scintillators in X-ray equipment
Curiosities
- One MRI scan in three worldwide uses gadolinium contrast.
- Gadolinium is ferromagnetic but loses it at 19 °C — in a warm room it is an ordinary paramagnet.
- Gadolinium-157 absorbs neutrons about 65 times more efficiently than boron-10.
- Gadolinium is the only element named after a Finnish chemist.