Berkelium . Chemical element atomic number 97, symbol Bk, the eighteenth member of the actinide series. In this series the 5f electronic layer is filled at the same time as in the lanthanides ( Rare Earths ) the 4f is being occupied. These two series of elements are very similar in chemical properties, and berkelium, except for minor differences in ionic radius, is very similar to its counterpart, Terbium .
Summary
[ hide ]
- 1 Discovery
- 2 Properties
- 1 Property Values
- 3 Abundance and natural state
- 4 Health effects
- 5 Environmental effects
- 6 See also
- 7 External links
- 8 Sources
Discovery
It was discovered in December 1949 by American chemists Glenn Theodore Seaborg, Stanley G. Thompson, and Albert Ghiorso in the laboratories of the University of California at Berkeley, from which its name comes.
Berkelium was the fifth transuranic element synthesized and was achieved by bombarding milligram quantities of 241Am with cyclotron-accelerated alpha particles.
The first isotope produced had a mass of 243 and a half-life of about 4.5 hours. Ten isotopes are currently known.
Properties
Berkelium is part of the Actinides group . Actinides that have a higher atomic number cannot be found in nature and their life span is shorter. All isotopes of the actinide group, including berkelium, are radioactive.
The state of berkelium in its natural form is solid. Berkelium is a brittle white chemical element and belongs to the group of actinides. The atomic number for berkelium is 97. The chemical symbol for berkelium is Bk.
Berkelium is a soft, silvery-white radioactive metal . The berkelium-249 isotope emits low-energy electrons and is therefore relatively safe to handle. However, it decays with a half-life of 330 days to Californium -249, which is a powerful and dangerous emitter of alpha particles.
This gradual transformation is an especially important issue to consider when studying the properties of elemental berkelium and its chemical compounds, since the formation of Californium not only produces chemical contamination, but also self-inflicted radiation damage, and self-heating caused by the alpha particles it emits.
Berkelium metal is chemically reactive, exists in two crystalline forms, and melts at 986ºC (1806ºF). It was discovered in 1949 by SG Thompson, A. Ghiorso, and GT Seaborg at the University of California at Berkeley and was named in honor of that city. Nine isotopes are known, whose mass fluctuates between 243 and 251 and whose half-life ranges between 1 hour and 1,380 years.
The easiest isotope of berkelium to produce is 249Bk, which undergoes beta decay with a half life of 314 days, and is a valuable source in the preparation of 249Cf. The isotope with the longest half-life is 247Bk (1380 years), but it is difficult to obtain in sufficient quantity to be applied to the study of its chemistry.
The existence of 249Bk with a half life of 314 days makes it possible to isolate the element in appreciable quantities in order to study its properties.
Berkelium has not yet been obtained in its elemental form, but it is likely to be expected to have the appearance of a silvery metal, easily soluble in dilute mineral acids and readily oxidizable by air or oxygen at elevated temperatures to form oxide.
In 1962 , an appreciable quantity (1 billionth of a gram) of a pure berkelium compound, berkelium chloride, was produced. X-ray diffraction methods have been used to identify various compounds of the element.
Like other actinide elements, berkelium tends to accumulate in the bone system.
The most stable isotope, 247 Bk, is the most stable and has a half-life of about 1,400 years. Due to its rarity it does not currently have commercial or technical applications.
Property Values
- Atomic Mass: 247 amu
- Melting Point: 1219 K
- Normal Reduction Potential: – 2.01 V Bk 3+
- First Ionization Energy: 601 kJ / mol
- Atomic Radius: 1.7 Å
- Ionic Radius: Bk +3= 0.97 Å
- Atomic Volume: 16.7 cm ³/ mol
- Polarizability: 22.7 Å ³
- Electronegativity (Pauling): 1.3
- Number of protons / electrons: 97
- Number of neutrons (Isotope 247-Bk): 150
- Oxidation numbers: +2, +3, +4
- Electronegativity: 1.3
- Ionization Energy (kJ.mol -1): 601
- Enthalpy of vaporization (kJ.mol -1): 310
- First Ionization Potential (eV): 6.23
- Electronic Configuration: 1s 22s 2 p 6 3s 2 p 6 d 10 4s 2 p 6 d 10 f 14 5s 2 p 6 d 10 f 8 6s 2 p 6 d 1 7s 2
Abundance and natural state
Berkelium is not found in the Earth’s crust because it does not have stable isotopes. It must be prepared by nuclear reactions using more abundant white elements. These reactions include bombardment with charged particles, irradiation with neutrons from high flux reactors, or production in a thermonuclear device.
It is an artificially created radioactive metallic element.
The main isotope of berkelium is berkelium-249, which is synthesized in minute quantities in a high flux nuclear reactor, especially at the Oak Ridge National Laboratory in Tennessee , United States, and at the Research Institute of Atomic Reactors in Dimitrovgrad , Russia . The production of the berkelium-247 isotope requires the irradiation of the scarce synthetic curium-244 isotope with high-energy alpha particles .
Since 1967, total berkelium production in the United States has been just over one gram. There is no practical application of berkelium outside of scientific research that is primarily focused on the synthesis of heavier transuranic elements and Transactinides .
In 2009 at Oak Ridge, a quantity of 22 milligrams of berkelium-249 was prepared by irradiation for 250 days followed by a 90-day purification process. This sample was used to first synthesize the element ununseptium in 2009 at the Joint Institute for Nuclear Research, Russia , after it was bombarded with calcium ions-48 ions for 150 days. This was the culmination of the collaboration between Russia and the United States for the synthesis of elements 113 to 118.
Health effects
Berkelium does not occur in nature , and has not been found in the earth’s crust, so there is no reason to consider its health hazard. However, all of its known isotopes are radioactive, and although they are only produced artificially in laboratories and handled by experts, here are some health hazards of radioactivity to be aware of:
The development of nuclear technology has been accompanied by both large and small releases of radioactivity into the atmosphere, soil, oceans, seas, and groundwater, showing up throughout the world in plant, animal and inert matter. Radiation passes from one species to another and concentrates through the food chain, subjecting other animals and humans to its damaging effects.
The greatest threat of radioactivity to life as we know it is the damage it causes to genetic material, the genetic makeup of all living species. Genetic damage from radiation exposure accumulates over lives and generations.
Even low dose exposures are carcinogenic after prolonged exposure. The current generation, the one now in the womb, and all those who follow can suffer from cancers, damaged immune systems, leukemias, miscarriages, stillbirths, deformities and fertility problems. While many of these health problems are on the rise, individuals cannot prove that the cause was either increased background radiation or specific exposure. Only epidemiological evidence is scientifically acceptable to impute the cause. Perhaps the most extreme consequence over time will simply be the total cessation of reproductive capacity. Radiation is a known cause of sterility.
Environmental effects
Berkelium does not occur in nature, and it has not been found in the earth’s crust, so there is no reason to consider its effects on the environment. However, all its known isotopes are radioactive, and although they are only produced artificially in laboratories and are handled by experts, if they were to affect the environment they would cause cancers, damage to the immune system, leukemias, spontaneous abortions, birth deaths, deformities and fertility problems in all affected living beings.
