Isotopes of californium
Encyclopedia
Californium
Californium
Californium is a radioactive metallic chemical element with the symbol Cf and atomic number 98. The element was first made in the laboratory in 1950 by bombarding curium with alpha particles at the University of California, Berkeley. It is the ninth member of the actinide series and was the...

(Cf) is an artificial element, and thus a standard atomic mass
Atomic mass
The atomic mass is the mass of a specific isotope, most often expressed in unified atomic mass units. The atomic mass is the total mass of protons, neutrons and electrons in a single atom....

 cannot be given. Like all artificial elements, it has no stable isotope
Stable isotope
Stable isotopes are chemical isotopes that may or may not be radioactive, but if radioactive, have half-lives too long to be measured.Only 90 nuclides from the first 40 elements are energetically stable to any kind of decay save proton decay, in theory...

s. The first isotope
Isotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...

 to be synthesized was 245Cf in 1950. There are 20 known radioisotopes ranging from 237Cf to 256Cf and one nuclear isomer
Nuclear isomer
A nuclear isomer is a metastable state of an atomic nucleus caused by the excitation of one or more of its nucleons . "Metastable" refers to the fact that these excited states have half-lives more than 100 to 1000 times the half-lives of the other possible excited nuclear states...

, 249mCf. The longest-lived isotope is 251Cf with a half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...

 of 900 years.

Californium-252

Fission neutrons of californium-252 have an energy range of 0 to 13 MeV with a mean value of 2.3 MeV and a most probable value of 1 MeV.

Table

nuclide
symbol
Z(p
Proton
The proton is a subatomic particle with the symbol or and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom, along with neutrons. The number of protons in each atom is its atomic number....

)
N(n
Neutron
The neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of...

)
 
isotopic mass (u)
 
half-life decay
mode(s)Abbreviations:
EC: Electron capture
Electron capture
Electron capture is a process in which a proton-rich nuclide absorbs an inner atomic electron and simultaneously emits a neutrino...


SF: Spontaneous fission
Spontaneous fission
Spontaneous fission is a form of radioactive decay characteristic of very heavy isotopes. Because the nuclear binding energy reaches a maximum at a nuclear mass greater than about 60 atomic mass units , spontaneous breakdown into smaller nuclei and single particles becomes possible at heavier masses...

daughter
isotope(s)
nuclear
spin
excitation energy
237Cf 98 139 237.06207(54)# 2.1(3) s SF
Spontaneous fission
Spontaneous fission is a form of radioactive decay characteristic of very heavy isotopes. Because the nuclear binding energy reaches a maximum at a nuclear mass greater than about 60 atomic mass units , spontaneous breakdown into smaller nuclei and single particles becomes possible at heavier masses...

(various) 5/2+#
β+
Beta decay
In nuclear physics, beta decay is a type of radioactive decay in which a beta particle is emitted from an atom. There are two types of beta decay: beta minus and beta plus. In the case of beta decay that produces an electron emission, it is referred to as beta minus , while in the case of a...

237Bk
α
Alpha decay
Alpha decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle and thereby transforms into an atom with a mass number 4 less and atomic number 2 less...

233Cm
238Cf 98 140 238.06141(43)# 21.1(13) ms SF (various) 0+
β+ (rare) 238Bk
α (rare) 234Cm
239Cf 98 141 239.06242(23)# 60(30) s
[39(+37-12) s]
α 235Cm 5/2+#
β+ (rare) 239Bk
240Cf 98 142 240.06230(22)# 1.06(15) min α (98%) 236Cm 0+
SF (2%) (various)
β+ (rare) 240Bk
241Cf 98 143 241.06373(27)# 3.78(70) min β+ (75%) 241Bk 7/2-#
α (25%) 237Cm
242Cf 98 144 242.06370(4) 3.49(15) min α (80%) 238Cm 0+
β+ (20%) 242Bk
SF (.014%) (various)
243Cf 98 145 243.06543(15)# 10.7(5) min β+ (86%) 243Bk (1/2+)
α (14%) 239Cm
244Cf 98 146 244.066001(3) 19.4(6) min α (99%) 240Cm 0+
EC
Electron capture
Electron capture is a process in which a proton-rich nuclide absorbs an inner atomic electron and simultaneously emits a neutrino...

 (1%)
244Bk
245Cf 98 147 245.068049(3) 45.0(15) min β+ (64%) 245Bk (5/2+)
α (36%) 241Cm
246Cf 98 148 246.0688053(22) 35.7(5) h α 242Cm 0+
EC (5×10−4%) 246Bk
SF (2×10−4%) (various)
247Cf 98 149 247.071001(9) 3.11(3) h EC (99.96%) 247Bk (7/2+)#
α (.04%) 243Cm
248Cf 98 150 248.072185(6) 333.5(28) d α (99.99%) 244Cm 0+
SF (.0029%) (various)
249Cf 98 151 249.0748535(24) 351(2) a α 245Cm 9/2-
SF (5×10−7%) (various)
249mCf 144.98(5) keV 45(5) µs 5/2+
250Cf 98 152 250.0764061(22) 13.08(9) a α (99.92%) 246Cm 0+
SF (.077%) (various)
251CfHigh neutron cross-section
Neutron cross-section
In nuclear and particle physics, the concept of a neutron cross section is used to express the likelihood of interaction between an incident neutron and a target nucleus. In conjunction with the neutron flux, it enables the calculation of the reaction rate, for example to derive the thermal power...

, tends to absorb neutrons
98 153 251.079587(5) 900(40) a α 247Cm 1/2+
252CfMost common isotope 98 154 252.081626(5) 2.645(8) a α (96.9%) 248Cm 0+
SF (3.09%)High neutron emitter, average 3.7 neutron
Neutron
The neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of...

s per fission
Nuclear fission
In nuclear physics and nuclear chemistry, nuclear fission is a nuclear reaction in which the nucleus of an atom splits into smaller parts , often producing free neutrons and photons , and releasing a tremendous amount of energy...

(various)
253Cf 98 155 253.085133(7) 17.81(8) d β- (99.69%) 253Es (7/2+)
α (.31%) 249Cm
254Cf 98 156 254.087323(13) 60.5(2) d SF (99.69%) (various) 0+
α (.31%) 250Cm
β-β- (rare) 254Fm
255Cf 98 157 255.09105(22)# 85(18) min β- (99.99%) 255Es (7/2+)
SF (.001%) (various)
α (10−5%) 251Cm
256Cf 98 158 256.09344(32)# 12.3(12) min SF (99%) (various) 0+
β- (1%) 256Es
α (10−6%) 252Cm
β-β- (rare) 256Fm

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