Californium is a chemical element that is classified as a actinide metal. It was discovered in 1950 by Stanley Thompson, Kenneth Street, Albert Ghiorso and Glenn Seaborg.
Discovery of the Californium
The californum was the sixth synthetic transuranic element of the actinide series that was discovered.
It was first produced by Stanley Thompson, Kenneth Street, Albert Ghiorso and Glenn Seaborg in 1950 in California, USA.
The researchers bombarded curium-242 with alpha particles at the 60-inch cyclotron in Berkeley, California. Each nuclear reaction created californium-245 (half-life of 44 minutes) and a neutron. The experiment produced only about 700,000 atoms of californium-245. This number of atoms is enough to make a cube with sides about 27 nanometres long. Chemical analysis showed that the new element had been made.
Californium was first isolated in macroscopic quantities by Burris Cunningham and Stanley Thompson in 1958 at the Materials Testing Reactor in Arco, Idaho, through prolonged irradiation (five years) of plutonium-239. Approximately 1.2 micrograms of californium and 0.6 micrograms of berkelium were synthesized.
The element is named after the US state of California and the University of California.
Appearance and Characteristics
Harmful effects:
Californium is harmful due to its radioactivity.
Characteristics:
- Californium is a synthetic radioactive silvery-white metal with moderate chemical reactivity.
- It is a relatively soft and malleable metal and can be easily cut with a razor blade.
- It slowly tarnishes in air to form oxide at room temperature.
- Californium-252 is a very strong neutron emitter.
Uses of californium
- Californium-252 (half-life of 2,645 years) is produced in nuclear reactors and has found a variety of uses.
- It is used as a neutron emitter, providing neutrons for the start-up of nuclear reactors.
- It has also been used as a target material to produce transcalifornium elements. Ununoctium, the heaviest of the elements, was produced when a californium target was bombarded with calcium ions.
- Californium-252 is used to treat cervical cancer. It is also used to analyze the sulfur content of petroleum and in neutron moisture meters to measure soil moisture content.
Abundance and isotopes
- Abundance in the Earth’s crust: none
- Abundance in the solar system: negligible
Source: Californium is a synthetic element and is not found naturally on Earth. - The spectrum of californium-254 has been observed in supernovae. Californium is produced in nuclear reactors by bombarding plutonium with neutrons and in particle accelerators.
- Isotopes: Californium has 20 isotopes with known half-lives, with mass numbers from 237 to 256. Californium has no natural isotopes. Its longest-lived isotopes are 251 Cf, with a half-life of 898 years, 249Cf with a half-life of 351 years, and 250Cf with a half-life of 13.08 years.
| Symbol | Cf |
| Atomic number | 98 |
| Valence | +4, +3 y +2 |
| Atomic weight | 251 |
| Boiling point (ºC) | 1470 |
| Melting point (ºC) | 900 |
| Density (Kg/m3) | 15100 |
| Atomic structure | [Rn] 5f10 7s2 |
Discover more elements in our periodic table.