Gadolinium was discovered in 1880 and isolated in 1886. It becomes a superconductor at a temperature below 1083K. It is a strong magnet at room temperature. Gadolinium (lll) are used as phosphors for a different purpose.
History and Discovery
Gadolinium was discovered in 18th century. In 1880, Jean Charles Galissard de Marignac studied the spectroscopic lines in gadolinite samples and cerite (silicate mineral group). He separated mineral oxides from cerite and named that new element ‘’gadolinia’’. Paul Emile Lecoq de Boisbaudran confirmed the discovery of new element in 1886. Boisbaudran named gadolinium after mineralogist Johan Gadolin and Marignac accepted the name. The pure form of gadolinium was first manufactured by Felix Trombe in 1935. They also found that gadolinium is more ferromagnetic than iron at low temperature [1].
Gadolinium
| Periodic Table Classification | Group n/a Period 6 |
|---|---|
| State at 20C | Solid |
| Color | Silvery white |
| Electron Configuration | [Xe] 4f7 5d1 6s2 |
| Electron Number | 64 |
| Proton Number | 64 |
| Electron Shell | 2, 8, 18, 25, 9, 2 |
| Density | 7.90 g.cm-3 at 20°C |
| Atomic number | 64 |
| Atomic Mass | 157.25 g.mol -1 |
| Electronegativity according to Pauling | 1.20 |
Occurrence
Gadolinium is abundant in the Earth crust and is present in around 6.2mg/kg of the earth’s crust. It is the main constituent of bastnaesite (three carbonate fluoride mineral) and monazite (reddish-brown phosphate mineral). It is also present in trace amount in gadolinite. In nature, gadolinium mostly exists in its oxidized forms. Gadolinium is mainly present in China, US, Brazil, Sri Lanka, India and Australia. It is isolated from its minerals through ion exchange and solvent extraction process. It can be produced through the reduction of anhydrous gadolinium fluoride with calcium metal [2].
Physical Characteristics
Gadolinium is silvery white in color. It can undergo deformation and is pliable in nature. It is ferromagnetic (elements forms permanent magnet) at a temperature below 20OC and paramagnetic (weakly attracted by external applied magnetic field) above this temperature. Gadolinium chemical symbol is Gd and atomic number is 64. Its atomic weight is 157.25. Gadolinium melting point is 1312OC and boiling point is 3000OC. Its density at room temperature is about 7.90 g/cm3.
Chemical Characteristics
Gadolinium is tarnished quickly in moist air and form gadolinium (lll) oxide. It combines with nitrogen, carbon, sulfur, phosphorous, boron, selenium, silicon and arsenic at high temperatures and forms binary compounds. It also combines with various elements to form Gd (lll) derivatives. Gadolinium is a strong reducing agent and can reduce oxides of several metals into their elements. Gadolinium is electropositive and react slowly with cold water and quickly react with hot water form gadolinium hydroxide. The metal is attacked by dilute sulfuric acid and form solution which contain colorless Gd (lll) ions. Gadolinium also reacts with halogens at temperature. At higher temperature, above 200OC, it forms halides, and four halides are white in color except iodide which is yellow in color. Gadolinium mostly exists in +3 oxidation state. Oxides dissolve in acid and forms salts like gadolinium (lll) nitrate [3].
Significance and Uses
- Gadolinium has metallurgic properties, improving the workability and resistance of iron, chromium and alloys.
- 157Gd is used to target tumours in neutron therapy.
- It is also used in nuclear marine propulsion system as the burnable poison.
- Paramagnetic behaviour of gadolinium making it useful for magnetic resonance imaging (MRI).
- Gadolinium as phosphor is used in imaging.
- Its compounds are used to make green phosphors for making color TV tubes.
- Gadolinium- 153 is used in quality assurance applications like line sources, calibration phantoms and produce an image of radioisotope distribution inside the patient.
- It is also used as gamma rays source in X-ray absorption measurement.
- Gd: Y3Al5O12 (gadolinium yttrium garnet) is used in microwave applications.
- Gadolinium gallium garnet is used for imitation of diamonds.
- It is also used as an electrolyte in solid oxide fuel cells (electrochemical conversion device).
- Its compounds are used as a research tool in biomedicine.
- Gadolinium is also used for making compact disks and computer memory.
Health Hazards
Gadolinium salts are irritable for skin and eyes. They have been linked with various tumours in some cases. But the toxicity of gadolinium has not been studied in detail.
Isotopes of Gadolinium
Gadolinium has six stable isotopes: 154Gd, 155Gd, 156Gd, 157Gd, 158Gd and 160Gd. Twenty nine radioisotopes also have been observed, the most stable is 152Gd with the half-life of 1.08 x 1014 years. 150Gd has 1.79 x 106 years. All remaining have half -lives less than 75 years. It also has metastable isomers: 143mGd with half- life 110 seconds, 145mGd (85 seconds) and 141mGd with 24.5 seconds half-life.
REFERENCES
[1]. https://www.chemicool.com/elements/gadolinium.html
[2]. Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements(2nd ed.). Butterworth-Heinemann. ISBN 0-08-037941-9