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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