326 | The History and Use of Our Earth’s Chemical Elements radioactive element of the actinide series by using the cyclotron to bombard americium-241
326 | The History and Use of Our Earth’s Chemical Elements radioactive element of the actinide series by using the cyclotron to bombard americium-241
with alpha particles (helium nuclei), resulting in the transmutation of the Am-241 to Bk-243 by adding not only two neutrons but also two protons to americium.
CommonUses Because such small amounts of berkelium have been produced, not many uses for it have
been found. One use is as a source for producing the element californium by bombarding isotopes of berkelium with high-energy neutrons in nuclear reactors. Berkelium is also used in some laboratory research.
ExamplesofCompounds Some berkelium compounds have been produced in fractions of a gram. For instance, a
sample of berkelium chloride (BkCl 3 ) was artificially produced. It weighed only three bil- lionths of a gram (0.00000003 grams). Since that time, several other compounds have been synthesized. Although difficult to produce, they are berkelium oxychloride (ByOCl), berkelium
fluoride (BkF 3 ), and berkelium trioxide (BkO 3 ).
Hazards Like the radioactive isotopes of berkelium, its compounds are also extremely dangerous
radioactive poisons. Because of the extremely small amounts of berkelium isotopes and com- pounds that exist and are produced, it is unlikely that many people will be exposed to them.
CALIFORNIUM SYMBOL:Cf PERIOD:7 SERIESNAME:Actinides ATOMICNO:98
ATOMICMASS:252amu VALENCE:3and4 OXIDATIONSTATE:+3and+4
NATURALSTATE:Solid ORIGINOFNAME:NamedforboththestateofCaliforniaandtheUniversityofCalifornia. ISOTOPES:Thereareatotalof21isotopesofcalifornium.Nonearefoundinnatureandall
areartificiallyproducedandradioactive.Theirhalf-livesrangefrom45nanosecondsfor californium-246to898yearsforcalifornium-251,whichisitsmoststableisotopeand whichdecaysintocurium-247eitherthoughspontaneousfissionorbyalphadecay.
ELECTRONCONFIGURATION EnergyLevels/Shells/Electrons Orbitals/Electrons
s2,p6
3-M=18
s2,p6,d10
4-N=32
s2,p6,d10,f14
5-O=28
s2,p6,d10,f10
6-P=8
s2,p6
7-Q=2
s2
327 Properties
Guide to the Elements |
Californium is a synthetic radioactive transuranic element of the actinide series. The pure metal form is not found in nature and has not been artificially produced in particle accelera- tors. However, a few compounds consisting of californium and nonmetals have been formed by nuclear reactions. The most important isotope of californium is Cf-252, which fissions spontaneously while emitting free neutrons. This makes it of some use as a portable neutron source since there are few elements that produce neutrons all by themselves. Most transuranic elements must be placed in a nuclear reactor, must go through a series of decay processes, or must be mixed with other elements in order to give off neutrons. Cf-252 has a half-life of 2.65 years, and just one microgram (0.000001 grams) of the element produces over 170 million neutrons per minute.
Californium’s melting point is ˜900°C, its boiling point is unknown, and its density is also unknown.
Characteristics Californium is a transuranic element of the actinide series that is homologous with dys-
prosium ( 66 Dy), just above it in the rare-earth lanthanide series. Cf-245 was the first isotope of californium that was artificially produced. It has a half-life of just 44 minutes. Isotopes of californium are made by subjecting berkelium to high-energy neutrons within nuclear reac- tors, as follows: 249 Bk + (neutrons and λ gamma rays) → 250 Bk → 250 Cf + β- (beta particle emission)
AbundanceandSource Neither californium nor its compounds are found in nature. All of its isotopes are produced
artificially in extremely small amounts, and all of them are extremely radioactive. All of its isotopes are produced by the transmutation from other elements such as berkelium and ameri- cium. Following is the nuclear reaction that transmutates californium-250 into californium- 252: 250 Cf + (neutron and λ gamma rays) → 251 Cf + (neutron and λ gamma rays) → 252 Cf.
History In 1950 the team of nuclear scientists at the University of California at Berkeley led
by Stanley Thompson, which included Kenneth Street, Jr., Albert Ghiorso, and Glenn T. Seaborg, artificially produced californium, which was the sixth transuranic element formed in their large cyclotron, by bombarding curium-242 with alpha particles (He ++ ). They had a dilemma with following their former precedence of naming their newly discovered elements with a name related to the elements’ analogues located in the rare-earth series above them in the lanthanide series. Therefore, since a term related to “dysprosium,” meaning “hard to find” did not seem to be appropriate for the new element in the actinide series, they named it after their laboratory and the state in which it was discovered.
CommonUses Californium’s uses are limited, which is why the U.S. Nuclear Regulatory Commission,
which controls the output and use of radioisotopes, has made californium-252 available for commercial use at the cost of only $10 per millionth of a gram. This small quantity is adequate for many sources of free neutrons to be used commercially. For example, free neutrons can
328 | The History and Use of Our Earth’s Chemical Elements
be used in devices to measure moisture in products, including the Earth’s crust, to find water or supplies of underground oil. Cf-252’s ability to produce neutrons has also found uses in medicine. Cf-252’s natural spontaneous fission makes it an ideal and accurate counter for electronic systems.
ExamplesofCompounds Only a few compounds of californium have been prepared. All are extremely radioactive
and have not found many common uses. Californium will combine with several nonmetals as follows: californium oxide (CfO 3 ), californium trichloride (CfCl 3 ), and californium oxychloride (CfOCl).
Hazards Californium’s greatest danger is as a biological bone-seeking radioactive element, which
can be both a radiation hazard and a useful treatment for bone cancer. If mishandled, all of californium’s isotopes and compounds can be a potential radiation poison.
EINSTEINIUM SYMBOL:Es PERIOD:7 SERIESNAME:Actinide ATOMICNO:99
ATOMICMASS:252amu VALENCE:2and3 OXIDATIONSTATE:+2and+3
NATURALSTATE:Solid ORIGINOFNAME:NamedafterandinhonorofthefamousphysicalscientistAlbertEinstein. ISOTOPES:Therearetotalof20isotopesofeinsteinium.Einsteiniumisnotfoundin
nature.Alltheisotopesareradioactiveandareproducedartificially.Theirhalf-livesrange fromeightsecondsto472days.Nonehaveexceptionallylonghalf-lives.
ELECTRONCONFIGURATION EnergyLevels/Shells/Electrons Orbitals/Electrons
s2,p6
3-M=18
s2,p6,d10
4-N=32
s2,p6,d10,f14
5-O=29
s2,p6,d10,f11
6-P=8
s2,p6
7-Q=2
s2
Properties Einsteinium belongs to group 13 (IIIA) of the heavy transuranic subseries of elements
found in the actinide series. It was discovered after World War II, sometime in 1952, as a trace element in the residue from the massive explosion of the hydrogen bomb on Eniwetok
329 Atoll in the Marshall Islands, located in the West Central Pacific Ocean. Although the atoll
Guide to the Elements |
was obliterated, literally wiped off the face of the Earth, several heavy elements, both known and unknown at that time, were detected in the aftermath of the explosion by a team of sci- entists led by Albert Ghiorso of the Berkeley laboratory. Einsteinium was one of these trace elements that was detected. Its existence, as well as several other discovered elements, was not announced until 1955, due to secrecy related to this new type of thermonuclear bomb. The melting and boiling points as well as the density of einsteinium are not known because of the extremely small amounts that have been produced.
Characteristics Einsteinium’s most stable isotope, einsteinium-252, with a half-life of 472 days, decays into
berkelium-248 through alpha decay, and then into californium-252 through beta capture. It can also change into fermium-252 through beta decay.
Einsteinium has homologous chemical and physical properties of the rare-earth holmium ( 67 Ho), located just above it in the lanthanide series in the periodic table.
AbundanceandSource Einsteinium does not exist in nature and is not found in the Earth’s crust. It is produced in
small amounts by artificial nuclear transmutations of other radioactive elements rather than by additional explosions of thermonuclear weapons. The formation of einsteinium from decay pro- cesses of other radioactive elements starts with plutonium and proceeds in five steps as follows:
1. 239 Pu →2 neutrons + gamma rays → 241 Pu → 241 Am + β-. 2. 241 Am → 1 neutron + gamma → 242 Am → 242 Cm + β-. 3. 242 Cm → 7 neutrons + gamma → 249 Cm → 249 Bk + β-. 4. 249 Bk → 1 neutron + gamma → 250 Bk → 250 Cf + β-. 5. 250 Cf → 3 neutrons + gamma → 253 Cf → 253 Es + β-.
History As mentioned, Einsteinium was first discovered in 1952 in residue material from the
first thermonuclear (hydrogen) bomb. The team that discovered this element included the Americans Gregory Choppin, Stanley Thompson, and Albert Ghiorso, as well as British physicist Bernard Harvey. This was a fusion (combining) nuclear reaction of heavy hydrogen (deuterium), wherein its nuclei were driven together by the great force of an atomic bomb inside the hydrogen bomb. This process is the opposite of fission nuclear reaction (splitting of heavy nuclei) as in the so-called atomic bombs. The explosion of this fusion bomb was the first time some of the heavier elements beyond uranium, including einsteinium and fermium, were formed by the following nuclear reaction: 238 U → 15 neutrons + gamma rays → 253 U → 7β- → 253 Es. Einsteinium, of course, was named after Albert Einstein to honor him for developing the concept that energy and matter are essentially the same, represented by his
famous formula E = mc 2 , which, in theory, made nuclear energy possible. CommonUses
Einsteinium does not really have any common uses except as related to research in nuclear and chemical laboratories.
330 | The History and Use of Our Earth’s Chemical Elements ExamplesofCompounds
Einsteinium, as an actinide metal, has several compounds similar to other transuranic ele- ments that are formed with some of the nonmetals, as follows: einsteinium dioxide (EsO 2 ), einsteinium trioxide (Es 2 O 3 ), einsteinium trichloride (EsCl 3 ), einsteinium dibromide (EsBr 2 ), and
einsteinium triiodide (EsI 3 ).
Hazards The radioisotopes of einsteinium are highly unstable and radioactive. The small amount of
the element and its compounds produced are not likely to be available in most laboratories. Thus, they do not pose any general hazard except in the case of scientists working with nuclear materials who must take precautions in handling exotic elements.
FERMIUM SYMBOL:Fm PERIOD:7 SERIESNAME:Actinides ATOMICNO:100
ATOMICMASS:257amu VALENCE:3 OXIDATIONSTATE:+3 NATURALSTATE:Solid ORIGINOFNAME:NamedafterandtohonorthescientistEnricoFermi. ISOTOPES:Thereareatotalof21isotopesoffermium.Theirhalf-livesrangefromfer-
mium-258’s370microsecondstofermium-257’s100.5days,whichisthelongestofall itsisotopes.Noneoffermium’sisotopesexistinnature.Allareartificiallyproducedand areradioactive.
ELECTRONCONFIGURATION EnergyLevels/Shells/Electrons Orbitals/Electrons
s2,p6
3-M=18
s2,p6,d10
4-N=32
s2,p6,d10,f14
5-O=30
s2,p6,d10,f12
6-P=8
s2,p6
7-Q=2
s2
Properties Fermium is the eighth transuranic element in the actinide series of group 14 (IVA) of the
periodic table. Similar to einsteinium, fermium was produced and discovered in the debris resulting from the explosion of the nuclear hydrogen bomb in 1952. Its existence was kept secret because of security measures that were established during World War II, thus keeping Albert Ghiorso and his colleagues at the University of California at Berkeley from receiv- ing credit for the discovery until 1955. Fermium’s melting point is thought to be about 1500+degrees Celsius, but its boiling point and density are unknown since so little of it is produced and because of the short half-lives of its isotopes.
331 Characteristics
Guide to the Elements |
The chemical characteristics of fermium are not very well known, but they are similar to its homologue erbium, the rare-earth element located just above it in the lanthanide series.
The nuclear reaction in the hydrogen bomb that produced fermium was the result of the acquisition of 17 neutrons by uranium from the explosion resulting in uranium-255 and some gamma radiation. U-255 decays by β-electron emission to form fermium-255, as depicted in
the equation as follows: 92 U-238 + 17 neutrons and gamma radiation → 92 U-255 → 100 Fm- 255 + the emission of 8 electrons.
AbundanceandSource Fermium does not exist in nature. All of it is artificially produced in cyclotrons, isotope
particle accelerators, or nuclear reactors by a very complicated decay process involving six steps of nuclear bombardment followed by the decay of beta particles, as follows:
1. Plutonium-239 (plus 2 neutrons) to 94 Pu-241 → americium-241+ β-. 2. Americium-241 (plus 1 neutron) to 95 Am-242 → to curium-242 + β-.
3. Curium-242 (plus 7 neutrons) to 96 Cm-249 → to berkelium-249 + β-.
4. Berkelium-249 (plus 7 neutrons) to 97 Bk-250 → to californium-250 + β-. 5. Califorium-250 (plus 3 neutrons) to 98 Ca-253 → to einsteinium-253 + β-. 6. Einstenium-253 (plus 1 neutron) to 99 Es-254 → to fermium-254 + β-.
History As mentioned, fermium was first detected in the debris of the hydrogen bomb. The ther-
monuclear fusion (hydrogen) bomb of 1952 is somewhat opposite of the fission (atomic) bomb. Whereas fission splits the nuclei of one element into nuclei of smaller elements, fusion combines the nuclei of heavy hydrogen (deuterium) into nuclei of the element helium and other elements. Both reactions produce tremendous amounts of energy and radiation, as well as many different subatomic particles. Today, fermium is synthesized by intense nuclear bom- bardment in the High Flux Isotope Reactor at Oak Ridge National Laboratory located in Oak Ridge, Tennessee, where plutonium (or uranium) undergoes a series of decays to end up as an isotope of fermium. (See previous section titled “Abundance and Source.”)
CommonUses Because such small amounts of fermium are produced and because the half-lives of its iso-
topes are so short, there are no commercial uses for it except for basic scientific research. ExamplesofCompounds
As with most other transuranic elements of the actinide series, fermium has an oxidation state of +3, as well as possibly a +2 oxidation state. Thus, this ion can combine with nonmet- als, such as oxygen and the halogens, as do many of the other elements in this series. Two examples follow:
Fermium oxide: 2Fm 3+ + 3O 2- → Fm 2 O 3. Fermium fluoride: Fm 3+ 3F 1- → FmF 3 .