Gadolinium - 64Gd: the essentials
- Name: gadolinium
- Symbol: Gd
- Atomic number: 64
- Relative atomic mass (Ar): 157.25 (3) g [see note g]
- Standard state: solid at 298 K
- Appearance: silvery white
- Classification: Metallic
- Group in periodic table:
- Group name: Lanthanoid
- Period in periodic table: 6 (lanthanoid)
- Block in periodic table: f
- Shell structure: 2.8.18.25.9.2
- CAS Registry: 7440-54-2
Gadolinium atoms have 64 electrons and the shell structure is 2.8.18.25.9.2. The ground state electronic configuration of neutral gadolinium is [Xe].4f7.5d1.6s2 and the term symbol of gadolinium is 9D2.
Gadolinium: description
Gadolinium is silvery white, has a metallic lustre, and is is malleable and ductile. It is ferromagnetic (strongly attracted by a magnet).
The metal is relatively stable in dry air, but in moist air it tarnishes with the formation of a loosely adhering oxide film which "spalls" off and exposes more surface to oxidation. The metal reacts slowly with water and is soluble in dilute acid. Gadolinium has the highest thermal neutron capture cross-section of any known element.
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Gadolinium: physical properties
Density of solid: 7901 kg m-3
Molar volume: 19.90 cm3
Thermal conductivity: 11 W m‑1 K‑1
Gadolinium: heat properties
Melting point: 1585 [1312 °C (2394 °F)] K
Boiling point: 3523 [3250 °C (5882 °F)] K
Enthalpy of fusion: 20.5 kJ mol-1
Gadolinium: atom sizes
Atomic radius (empirical): 180 pm
Molecular single bond covalent radius: 169 (coordination number 3) ppm
van der Waals radius: 279 ppm
Gadolinium: electronegativities
Pauling electronegativity: 1.20 (Pauling units)
Allred Rochow electronegativity: 1.11 (Pauling units)
Mulliken-Jaffe electronegativity: (no data)
Gadolinium: orbital properties
First ionisation energy: 593.37 kJ mol‑1
Second ionisation energy: 1165.2 kJ mol‑1
Third ionisation energy: 1980 kJ mol‑1
Gadolinium: abundances
Universe: 2 ppb by weight
Crustal rocks: 5200 ppb by weight
Human: (no data) ppb by weight
Gadolinium: crystal structure
Gadolinium: biological data
- Human abundance by weight: (no data) ppb by weight
Gadolinium has no biological role but is said to stimulate the metabolism.
Gadolinium: uses
Gadolinium: reactions
Reactions of gadolinium as the element with air, water, halogens, acids, and bases where known.
Gadolinium: binary compounds
Binary compounds with halogens (known as halides), oxygen (known as oxides), hydrogen (known as hydrides), and other compounds of gadolinium where known.
Gadolinium: compound properties
Bond strengths; lattice energies of gadolinium halides, hydrides, oxides (where known); and reduction potentials where known.
Gadolinium: history
Gadolinium was discovered by Jean de Marignac in 1880 at Switzerland. Origin of name: named after J. "Gadolin", a Finnish chemist and minerologist.Gadolinium: isotopes
Gadolinium has the highest cross section for the capture of thermal neutrons of any element and this is mainly due to the high cross section of Gd-157 (255,000 barn) and Gd-155 (61,000 barn). Natural Gadolinium is currently used as a burnable poison in nuclear fuel, but the use of Gd-155/157 only has been proposed as this would create an even more effective burnable poison. Gd-152 is used for the production of radioactive Gd-153 which is used for osteoporosis research and bone density measurements. Gd-160 is used in double beta decay research.
Gadolinium: isolation
Isolation: gadolinium metal is available commercially so it is not normally necessary to make it in the laboratory, which is just as well as it is difficult to isolate as the pure metal. This is largely because of the way it is found in nature. The lanthanoids are found in nature in a number of minerals. The most important are xenotime, monazite, and bastnaesite. The first two are orthophosphate minerals LnPO4 (Ln deonotes a mixture of all the lanthanoids except promethium which is vanishingly rare) and the third is a fluoride carbonate LnCO3F. Lanthanoids with even atomic numbers are more common. The most comon lanthanoids in these minerals are, in order, cerium, lanthanum, neodymium, and praseodymium. Monazite also contains thorium and ytrrium which makes handling difficult since thorium and its decomposition products are radioactive.
For many purposes it is not particularly necessary to separate the metals, but if separation into individual metals is required, the process is complex. Initially, the metals are extracted as salts from the ores by extraction with sulphuric acid (H2SO4), hydrochloric acid (HCl), and sodium hydroxide (NaOH). Modern purification techniques for these lanthanoid salt mixtures are ingenious and involve selective complexation techniques, solvent extractions, and ion exchange chromatography.
Pure gadolinium is available through the reduction of GdF3 with calcium metal.
2GdF3 + 3Ca → 2Gd + 3CaF2
This would work for the other calcium halides as well but the product CaF2 is easier to handle under the reaction conditions (heat to 50°C above the melting point of the element in an argon atmosphere). Excess calcium is removed from the reaction mixture under vacuum.