Gadolinium

64

Gd

157.25(3)

  • Name: Gadolinium
  • Symbol: Gd
  • Atomic number: 64
  • Atomic weight: 157.25(3)
  • CAS Registry ID: 7440-54-2
  • Group name: Lanthanoid
  • Period number: 6
  • Block: f-block
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Description

Gadolinium is a lanthanide that has a bright, reflective, silvery white appearance in its natural solid state. It is stable in dry air but will tarnish in moist air; it also reacts slowly with water. Gadolinium has an atomic weight of 157.25, a melting point of 2394 °F, and a boiling point of 5923 °F. Some common uses of gadolinium include: as a component in microwaves, as a burnable poison in nuclear marine propulsion, to improve the workability of some metals, and in MRI and x-ray imaging.

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Isolation

Gadolinium does not occur free in nature, but is found in most minerals which also contain other lanthanides. Extraction processes can be used to isolate gadolinium from these minerals.

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The extraction and isolation processes of gadolinium are very complex. Gadolinium occurs in minerals such as monazite and bastnasite with other lanthanides that have similar chemical characteristics. The complex steps that must be used to separate these lanthanides is never performed on a small scale laboratory basis as it is just too difficult.

The isolation process of gadolinium involves treating the minerals it occurs in with sulfuric acid, hydrochloric acid, and sodium hydroxide. This process separates out the lanthanides from the minerals in their salt forms. Repeated solvent extractions and ion exchange chromatography are used to further separate the lanthanides from each other. Once gadolinium is reduced to its fluoride form, it can be reduced further by reacting it with pure calcium metal under heated conditions. Excess calcium that remains with the gadolinium is removed through vacuum processes yielding pure gadolinium. Gadolinium, like most lanthanides, has slightly toxic traits and should be handled with caution.


General
Name Gadolinium
Symbol Gd
Number 64
Chemical series lanthanides
Group n/a
Period 6
Block f
Appearance silvery white
Standard atomic weight 157.25(3)  g·mol−1
Electron configuration [Xe] 4f7 5d1 6s2
Electrons per shell 2, 8, 18, 25, 9, 2
Atomic properties
Crystal structure hexagonal
Oxidation states 3 (mildly basic oxide)
Electronegativity 1.20 (scale Pauling)
Ionization energies 1st:  593.4  kJ·mol−1
(more) 2nd:  1170  kJ·mol−1
(more) 3rd:  1990  kJ·mol−1
Atomic radius 180  pm
Atomic radius (calc.) 233  pm
Covalent radius
Van der Waals radius
Physical properties
Phase solid
Density (near r.t.) 7.90  g·cm−3
Liquid density at m.p. 7.4  g·cm−3
Melting point 1585 K (1312 °C, 2394 °F)
Boiling point 3546 K (3273 °C, 5923 °F)
Critical point
Heat of fusion 10.05  kJ·mol−1
Heat of vaporization 301.3  kJ·mol−1
Heat capacity (25 °C) 37.03  J·mol−1·K−1
Miscellaneous
Magnetic ordering ferromagnetic
Electrical resistivity (r.t.) (α, poly) 1.310 µΩ·m
Thermal conductivity (300 K) 10.6  W·m−1·K−1
Thermal expansion (100 °C) (α, poly) 9.4 µm/(m·K)
Speed of sound (thin rod) (20 °C) 2680 m/s
Young's modulus (α form) 54.8  GPa
Shear modulus (α form) 21.8  GPa
Bulk modulus (α form) 37.9  GPa
Poisson ratio (α form) 0.259
Mohs hardness
Vickers hardness 570  MPa
Brinell hardness
CAS registry number 7440-54-2

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