What is Berkelium?
Berkelium is a chemical element with atomic number 97 and symbol Bk. This transuranic chemical element is radioactive in nature. It was the fifth transuranium element discovered after curium, americium, plutonium, and neptunium. This chemical element is a member of the actinide and transuranium element series of the periodic table of elements. Bk element belongs to the period 7th and F-block of the periodic table. This metal remains in the solid-state at standard temperature and pressure. The atomic mass of this radioactive metal is 247. The electronic configuration of berkelium is [Rn] 5f97s2. The basic details of this chemical element are as follows.
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The above image shows the position of berkelium in the periodic table.
Discovery
Berkelium was first synthesized at the University of California, Berkeley (United States)in Dec 1949. Glenn T. Seaborg, Kenneth Street, Jr., Stanley G Thompson, and Albert Ghiorso first produced this radioactive metal. The team at the University of California used a 60-inch cyclotron for this experiment. First of all, these scientists coated the americium nitrate solution on a platinum foil. Then, they evaporated this solution to convert the residue in americium dioxide by annealing. Finally, their team irradiated the target in the 60-inch cyclotron with alpha particles for 6 hours. This experiment leads to the formation of the Berkelium-243 isotope along with two free neutrons.
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The IUPAC officially declared the name of this element as berkelium after the state of its discovery, Berkeley.
Occurrence
The half-lives of all the known isotopes of berkelium are too short. Hence, no primordial berkelium could not have survived by now from the formation of the earth. Bk is present on earth’s surface only in some areas mostly at the sites of nuclear incidents. The place where the individuals did the testing of atmospheric nuclear weapons between 1945 to 1980 also contains this element. The place where the first U.S. tested the first hydrogen bomb comprises high concentrations of several actinides including berkelium. Nuclear reactors also produce this radioactive element during the process.
Properties of Berkelium
Berkelium is a soft metal that is silvery-white in color. This radioactive metal is present below the lanthanide terbium with which it shares its many characteristics. The density of this chemical element is 14.78g/cm3 whose value lies between that of curium and californium. Similarly, the melting point of this metal is 986oC which is higher than curium but less than californium. The bulk modulus of Bk is 20 GPa which is one of the lowest among the actinides. This chemical element behaves as a paramagnetic material between 70 K and room temperature. A neutral atom of Bk has an ionization potential of around 6.23eV.
Bk dissolves in several aqueous inorganic acids like all actinides to liberate hydrogen gas. The most stable oxidation state of this metal is the trivalent oxidation state (+3) mostly in aqueous solutions. The other known oxidation states of berkelium compounds are divalent (+2) and tetravalent (+4) ones. There is still uncertainty about the presence of divalent berkelium salts.
At room temperature, the reaction of berkelium with oxygen doesn't take place because of the formation of the protective oxide layer surface. However, Bk can react with molten metals, chalcogens, halogen, hydrogen to form several binary compounds. In most of the acids, the Bk3+ ions are present in green colour. In sulphuric acid, the colour of Bk4+ atoms is orange-yellow, whereas it is yellow in hydrochloric acid.
Isotopes of Berkelium
At present, researchers have found about 20 isotopes of berkelium. The mass number of these isotopes ranges from 233 to 253 (except 235, 237, and 239) in which six are nuclear isotopes. All of the known isotopes of berkelium are radioactive whose half-lives range from microseconds to several days. 247Bk has the longest half-lives among all known isotopes of Bk, which is around 1380 years. The other known isotopes of Bk with long half-lives are 248Bk and 249Bk. The half-life of 248Bk is around 300 years, and 249Bk has a half-life of about 330 days.
249Bk is the easiest to synthesise isotope of the Bk element. The soft β-particles emitted by this isotope are inconvenient for detection. It also emits alpha radiation which is weak as compared to the β-radiation. However, this radiation can be useful in the detection of this isotope. The second most crucial isotope of this radioactive metal is 247Bk. It is also an alpha-particle emitter like the isotopes of most of the actinides.
FAQs on Berkelium
1. What Are The Important Uses Of Berkelium?
The formation of berkelium is expensive and limited too. Hence, it doesn't have any important applications in daily life. Scientists mostly use these radioactive elements and their isotopes for research purposes. Researchers use it for the synthesis of heavier chemical elements in the transuranic series. It is also an essential source for the production of californium-249, which is beneficial to study the properties of californium. A 22mg berkelium synthesised at Oak Ridge National Laboratory was extremely helpful in the discovery of element 117. Bk element doesn't occur in nature due to which scientists need to produce it in labs artificially.
2. What Are The Health Issues Of Berkelium?
Scientists are not able to produce Bk in significant amounts until now. Hence, the health effects of this radioactive metal on the human body are still unclear. According to the predictions, the isotope 249Bk is harmless as compared to other actinides as it emits electrons of low energy. However, this isotope will transform into californium-249 after the decay, which can be extremely dangerous. The ingestion of Bk by rats can cause cancer in various organs according to the research. Moreover, the radiation after the ingestion can also damage red blood cells in the skeletal system.