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Californium

From Academic Kids

berkeliumcaliforniumeinsteinium
Dy
Cf
  
 
 
Image:-TableImage.png
Known properties
Name, Symbol, NumberCalifornium, Cf, 98
Chemical series Actinides
Period, Block7, f
Appearance unknown; probably metallic,
silvery white or gray
Atomic weight [251] amu
Electron configuration [Rn]5f107s2
e-'s per energy level 2,8,18,32,28,8,2
State of matter solid
Most stable isotopes
isoNAhalf-life DMDE MeVDP
248Cf{syn.}333.5 d SF
α

6.361

244Cm
249Cf{syn.}351 ySF
α

6.295

245Cm
250Cf{syn.}13.08 yα
SF
6.128

246Cm

251Cf{syn.}898 yα6.176247Cm
252Cf{syn.}2.645 yα
SF
6.217
 
248Cm
 
253Cf{syn.}17.81 dβ-
α
0.285
6.124
253Es
249Cm
254Cf{syn.}60.5 dSF
α
 
5.926
 
250Cm

Californium is a synthetic element in the periodic table that has the symbol Cf and atomic number 98. A radioactive transuranic element, californium has very few uses and was discovered by bombarding curium with alpha particles (helium ions).

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Contents

Notable characteristics

Weighable amounts of californium make it possible to determine some of its properties using macroscopic quantities.

Californium-252 (half-life 2.6 years) is a very strong neutron emitter and is thus extremely radioactive and harmful (one microgram spontaneously emits 170 million neutrons per minute). The decay of californium-254 (55-day half-life) may have been detected through telescopes in supernovae remnants. Californium-249 is formed from the beta decay of berkelium-249 and most other californium isotopes are made by subjecting berkelium to intense neutron radiation in a nuclear reactor.

The element does have some specialist applications dealing with its radioactivity but otherwise is largely too difficult to produce to have useful significance as a material. Two of its few uses;

As of 2004, californium has not been isolated in its metallic form. The only californium ion that is stable in aqueous solution is californium (III). Californium has no biological role and only a few californium compounds have been made and studied. Included among these are: californium oxide (CfO3), californium trichloride (CfCl3) and californium oxychloride (CfOCl).

Californium-251 is famous for having a very small critical mass, creating speculation about possible use in pocket nukes although this urban legend is unfounded since it would be very difficult to make a Californium-251 bomb weighting less than 2kg and the costs of such bomb would be prohibitive.

History

Californium was first synthesized by University of California, Berkeley researchers Stanely Thompson, Kenneth Street, Jr., Albert Ghiorso and Glenn T. Seaborg in 1950. It was the sixth transuranium element to be discovered and the team announced their discovery on March 17, 1950. It was named after the U.S. state of California and for the University of California, Berkeley (which is nicknamed "Cal").

To produce element 98, the team bombarded a microgram-sized target of curium-242 with 35 MeV alpha particles in the 60-inch Berkeley cyclotron to produced atoms of californium-245 (half-life 44 minutes) and a free neutron.

Isotopes

19 radioisotopes of californium have been characterized, with the most stable being Cf-251 with a half-life of 898 years, Cf-249 with a half-life of 351 years, and Cf-250 with a half-life of 13 years. All of the remaining radioactive isotopes have half-lifes that are less than 2.7 years, and the majority of these have half lifes that are less than 20 minutes. The isotopes of californium range in atomic weight from 237.062 amu (Cf-237) to 256.093 amu (Cf-256).

References

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