Berkelium is a transuranic element synthesized and identified in December 1949 by Glenn. T Seaborg, Albert Ghiorso, Stanley G. Thompson and Kenneth Street, Jr. It is a radioactive element with not much uses outside basic scientific research.
History and Discovery
Berkelium was first intentionally synthesized by Glenn T. Seaborg, Stanley G. Thompson, Albert Ghiorso and Kenneth Street, Jr. in December 1949 using the 60-inch cyclotron at University of California, Berkeley [1]. Berkelium was named after the city of Berkeley, California like the element above it in lanthanide series was named terbium after the town of Ytterby, Sweden, where the rare earth minerals were first found. It is the fifth transuranic element discovered.
Berkelium
| Periodic Table Classification | Group n/a Period 7 |
|---|---|
| State at 20C | Solid |
| Color | Silvery |
| Electron Configuration | [Rn] 5f9 7s2 |
| Electron Number | 97 |
| Proton Number | 97 |
| Electron Shell | 2, 8, 18, 32, 27, 8, 2 |
| Density | 14.78 g.cm-3 at 20°.C |
| Atomic number | 97 |
| Atomic Mass | 247.00 g.mol -1 |
| Electronegativity according to Pauling | 1.30 |
Occurrence
Berkelium can be found on earth concentrated in areas where atmospheric nuclear tests were conducted or at areas where nuclear disaster took place. Berkelium, along with other actinides, was also found in high concentration at the testing site of first U.S hydrogen bomb. It is produced in nuclear reactors particularly the isotope berkelium-249. Berkelium isotopes have a relatively short half-life indicating any primordial berkelium would have decayed by now.
Physical Characteristics
Berkelium is silvery white in colour and a relatively soft metal. Its bulk modulus is one of the lowest amongst the actinides. Its physical properties resembles to that of its neighbouring elements. Its density and melting point lies between curium and californium. It has a melting point of 986 degree centigrade and has a density of 14.78 g/cm3. Due to internal transition, berkelium ions show two sharp fluorescence peaks [2]. Berkelium behaves as a paramagnetic material at room temperature and low temperatures. At very low temperature (-239 degree centigrade or less) it undergoes transition to an antiferromagnetic state. Berkelium has an atomic number 97 and is represented by symbol Bk.
Chemical Characteristics
Berkelium is a radioactive element. It dissolves in numerous aqueous inorganic acids like all other actinides. In aqueous solutions +3 is the most stable oxidation state while it readily adopts oxidation state of +4 in solids [3]. Its chemical properties resemble to its neighbouring element in lanthanide series named terbium. Berkelium forms a protective oxide layer surface and does not rapidly react with oxygen at room temperature although it does react with molten metals forming various binary compounds.
Significance and Uses
- Berkelium has currently no known uses apart from its use in basic scientific research. It is produced in small quantity as required and is commonly used to make heavier transuranic elements and trans-actinides.
Health Effects
Not much is known about the health effects of berkelium because of it being a rare element. Berkelium-249 isotope is safe to handle since it emits low energy electrons. Its low energy radiation hinders its detection. It has a short half-life of 330 days and decays into californium-249 which is a strong alpha emitter and could be dangerous for human body. Berkelium if ingested can absorb in human body and can eventually promote cancer.
Isotopes of Berkelium
Berkelium has twenty known isotopes with mass number ranging from 235 to 254 with no stable isotope. The isotope with longest half-life is berkelium-247 with half-life of 1380 years. Berkelium-248 has a half-life of 300 years while berkelium-249 has a half-life of 330 days. All other isotopes have half-life ranging from several days to few microseconds [4]. Berkelium-247 is an alpha emitter while berkelium-249 emits soft beta particles along with weak alpha radiations.
REFERENCES
[1]. Thompson, Stanley G.; Seaborg, Glenn T. (1950). “Chemical Properties of Berkelium”. doi:10.2172/932812. Archived from the original on 18 August 2011.
[2]. Itie, J. P.; Peterson, J. R.; Haire, R. G.; Dufour, C.; Benedict, U. (1985). “Delocalisation of 5f electrons in berkelium-californium alloys under pressure”. Journal of Physics F: Metal Physics. 15 (9): L213.
[3]. Fuger, J.; Haire, R. G.; Peterson, J. R. (1981). “A new determination of the enthalpy of solution of berkelium metal and the standard enthalpy of formation of Bk3+ (aq)”. Journal of Inorganic and Nuclear Chemistry. 43(12): 3209
[4]. Peterson, J. R.; Fahey, J. A.; Baybarz, R. D. (1971). “The crystal structures and lattice parameters of berkelium metal”. J. Inorg. Nucl. Chem. 33 (10): 3345–51