Californium is a radioactive element and was synthesized for the first time in 1950. It is used to produce other heavier elements, such as oganesson. It is highly radioactive and requires proper handling to avoid hazardous health effects.
History and Discovery
Californium was first synthesized by team of researchers, including Albert Ghiorso, Thompson Kenneth Street, Glenn T and Stanley Thompson, working at the Lawrence Berkeley National Laboratory in 1950 [1]. It was prepared by bombarding curium with helium-4 ions (alpha particles). Californium is considered as the second element that has been produced in large enough amount to be seen with naked eyes. It is the sixth trans-uranium element (element with atomic number greater than 92), that has been synthesized. The name californium was given in honour of California University and the state California.
Californium
| Periodic Table Classification | Group n/a Period 7 |
|---|---|
| State at 20C | Solid |
| Color | Silvery |
| Electron Configuration | [Rn] 5f10 7s2 |
| Electron Number | 98 |
| Proton Number | 98 |
| Electron Shell | 2, 8, 18, 32, 28, 8, 2 |
| Density | 15.10 g.cm-3 at 20°C |
| Atomic number | 98 |
| Atomic Mass | 251.00 g.mol -1 |
| Electronegativity according to Pauling | 1.3 |
Occurrence
Californium is a rare element. It is not found in significant quantity in the earth’s crust. Californium is present in trace amounts near laboratories and medical facilities where it is being used for various purposes. It has also been introduced into the environment through nuclear testing, as it is produced in nuclear reactors [2]. Californium-235 is produced as a result of series of neutron capturing by uranium-238 [3].
Physical Characteristics
Californium is a whitish silver metal that belongs to the lanthanide metal series of the periodic table. Californium has three allotropic forms that vary according to pressure. The boiling point of californium is predicted to be around 1470°C and its melting point is expected to be around 900°C. In its pure form, californium is quite soft and malleable, as it can be easily cut with a knife. When exposed to high temperature (above 300°C in vacuum), it is transformed into vapor state. Californium is insoluble in water.
Chemical Characteristics
Californium reacts slowly with oxygen and air and tarnishes at room temperature. The most common oxidation state of californium is +3. Chemically, californium resembles dysprosium and other elements of the actinide series that have +3 oxidation state. Californium readily reacts with nitrogen, hydrogen and chalcogens. It also dissolves in mineral acids and the reaction is fast.
Significance and Uses
- Californium is used as trigger for nuclear reactors.
- It is used as neutron source for research and study purposes.
- Californium is used to synthesize various high mass elements, for instance oganesson was synthesized by bombarding calcium ions on californium-249 atoms.
Health Hazards
Californium is a biohazardous element as its radioactivity can cause serious consequences. The radiological effects of californium can lead to destruction of red bloods [4]. The gamma emission of californium-251 can lead to liver and bone cancer.
Isotopes of Californium
There are twenty known isotopes of californium, with atomic masses ranging from 237 to 256 [4]. And the most stable is californium-251 that has a half-life of 898 years. Californium-252 is the most widely produced and used isotope, and it has a half-life of 2.64 years. It emits neutrons with great intensity and have the highest radioactivity among all other isotopes of californium. Californium-252 primarily undergoes alpha decay and very rarely decay through spontaneous fission. Another isotope, californium-249 is produced during the beta decay of berkelium-249.
REFERENCES
[1]. Cunningham 1968, p. 103
[2]. Krebs 2006, pp. 327–328
[3]. NRC 2008, p. 33.
[4]. Cunningham 1968, p. 106
[5]. NNDC contributors (2008). Sonzogni, Alejandro A. (Database Manager), ed. “Chart of Nuclides”. National Nuclear Data Center, Brookhaven National Laboratory.