Europium was discovered in 1800s but isolated for the first time in 1901. It readily oxides in water and air. It has been used as doping agent in glass. It is also included in the study of geochemistry and petrology to study the process of the formation of igneous rocks.
History and Discovery
Europium is present in the ores of many minerals but till 1800s it was not isolated from minerals. Paul Emile Lecoq de Biosbaurdran was first who observed it in basic fractions from samarium-gadolinium concentrate in 1892. Later, in 1901 Eugene-Anatole Demarcay discovered europium, and isolated it as a contaminant from samarium. He named it europium after the continent Europe [1].
Europium
| Periodic Table Classification | Group n/a Period 6 |
|---|---|
| State at 20C | Solid |
| Color | Silvery white, with a pale yellow tint |
| Electron Configuration | [Xe] 4f7 6s2 |
| Electron Number | 63 |
| Proton Number | 63 |
| Electron Shell | 2, 8, 18, 25, 8, 2 |
| Density | 5.24 g.cm-3 at 20°C |
| Atomic number | 63 |
| Atomic Mass | 151.96 g.mol -1 |
| Electronegativity according to Pauling | 1.20 |
Occurrence
Europium is not found in free or elemental form in nature. It is obtained from many minerals like: bastnasite (family of three carbonate fluoride mineral), monazite (reddish brown phosphate mineral), xenotime (phosphate mineral) and loparite-(Ce) (granular brittle oxide mineral). It occurs in the products of the nuclear fission [2]. Its minerals deposits are found in China.
Physical Characteristics
Europium is moderately hard and silvery metal. It is flexible in nature, its hardness is similar with the lead. Europium chemical symbol is Eu. Its atomic number is 63. Atomic weight of Europium is 151.964. Its melting point is 826OC which is the second lowest melting point. Its boiling point is 1529OC. It has low density at room temperature which is about 5.264 g/cm3. It becomes a superconductor when it is cooled below 1.8 K. Europium is divalent at metallic state and trivalent when pressure is applied.
Chemical Characteristics
Europium is highly reactive rare earth metal of the lanthanide series. It is quickly tarnished when exposed to air. Its oxidation of a centimeter-sized sample occurs within days. It is silvery in color but becomes dull when exposure to air. It reacts quickly with water and its reactivity is similar with calcium. It reacts with dilute acids except hydrofluoric acid (HF) due to the formation of protective layer of EuF3. Europium is at 90 K act as strong paramagnet and below that temperature it is antiferromagnetically. It ignites in air at 150 to 180OC and form europium (lll) oxide. It is mostly exist in +3 oxidation state but +2 is also common. Europium (ll) and barium (ll) are similar in nature and their sulfates are insoluble in water. It reacts with all halogens forms white EuF3, yellow EuCl3, gray EuBr3 and colorless EuI3. It is also forms dihalides [3].
Significance and Uses
- Europium is used as a doping agent in glass, laser and optoelectronic devices.
- Its oxides Eu2O3 is widely used as red phosphor in television sets and fluorescent lamps.
- It is also used in the preparation of fluorescent glass.
- Europium fluorescence are used to interrogate in drug discovery screen for bimolecular interaction.
- Eu(fod)3 is used as shift reagent in NMR (Nuclear magnetic resonance) spectroscopy.
- Europium is also used in quantum memory chips which can store data for days at a time.
- It is used in nuclear reactors control rods.
- Europium is added in mercury vapor lamp to give more natural street lights
- Europium salts are used for newer phosphorescent paints and powders.
- It is used in euro bank notes.
- Europium is widely used in making thin super conducting alloys.
- It is used as a source of blue light in light emitting diodes (LEDs).
Health Effects
Europium in the form of salts may be mildly toxic. However, it has no known biological role.
Isotopes of Europium
Europium naturally has two isotopes: 151Eu and 153Eu. 153Eu is stable while 151Eu is unstable having half-life of 5 -3+11 x 1018 years. It has thirty five artificial radioisotopes in which 150Eu has half-life of 36.9 years. 152Eu has 13.516 years, 154Eu has 8.593 years. All remaining have lives shorter than 4.7612 years.
REFERENCES
[1]. Demarçay, Eugène-Anatole (1901). “Sur un nouvel élément l’europium”. Comptes rendus. 132: 1484–1486.
[2]. https://en.wikipedia.org/wiki/Europium
[3]. Chemical reactions of Europium”. Webelements. Retrieved 2009-06-06