Curium

Curium

Curium is a synthetic chemical element with the symbol Cm and atomic number 96. This radioactive transuranic element of the actinide series was named after Marie Skłodowska-Curie and her husband Pierre Curie. Curium was first intentionally produced and identified in summer 1944 by the group of...

(Cm) 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 isotopes. 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...

 synthesized was ²⁴²Cm in 1944.

There are 21 known radioisotopes with 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....

es ranging from ²³²Cm to ²⁵²Cm. There are also four known 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...

s (^243mCm, ^244mCm, ^245mCm, and ^249mCm). The longest-lived isotope is ²⁴⁷Cm, 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 15.6 million years. The longest-lived isomer is ^244mCm with a half-life of 34 milliseconds.

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 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...	decay mode(s)Abbreviations: CD: Cluster decay Cluster decay Cluster decay is a type of nuclear decay in which a parent atomic nucleus with A nucleons and Z protons emits a cluster of Ne neutrons and Ze protons heavier than an alpha particle but lighter than a typical binary fission fragment Cluster decay (also named heavy particle radioactivity or heavy... 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... IT: Isomeric transition Isomeric transition An isomeric transition is a radioactive decay process that involves emission of a gamma ray from an atom where the nucleus is in an excited metastable state, referred to in its excited state, as a nuclear isomer.... 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 isotopesBold for stable isotopes	spin
	excitation energy
232Cm	96	136		1? min			0+
233Cm	96	137	233.05077(8)	1# min	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...	233Am	3/2+#
					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...	229Pu
234Cm	96	138	234.05016(2)	51(12) s	β+	234Am	0+
					α	230Pu
235Cm	96	139	235.05143(22)#	5# min	β+	235Am	5/2+#
					α	231Pu
236Cm	96	140	236.05141(22)#	10# min	β+	236Am	0+
					α	232Pu
237Cm	96	141	237.05290(22)#	20# min	β+	237Am	5/2+#
					α	233Pu
238Cm	96	142	238.05303(4)	2.4(1) h	EC Electron capture Electron capture is a process in which a proton-rich nuclide absorbs an inner atomic electron and simultaneously emits a neutrino...  (90%)	238Am	0+
					α (10%)	234Pu
239Cm	96	143	239.05496(11)#	~2.9 h	β+ (99.9%)	239Am	(7/2-)
					α (.1%)	235Pu
240Cm	96	144	240.0555295(25)	27(1) d	α (99.5%)	236Pu	0+
					EC (.5%)	240Am
					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...  (3.9×10−6%)	(various)
241Cm	96	145	241.0576530(23)	32.8(2) d	EC (99%)	241Am	1/2+
					α (1%)	237Pu
242CmMost common isotopes	96	146	242.0588358(20)	162.8(2) d	α	238Pu	0+
					SF (6.33×10−6%)	(various)
					CD Cluster decay Cluster decay is a type of nuclear decay in which a parent atomic nucleus with A nucleons and Z protons emits a cluster of Ne neutrons and Ze protons heavier than an alpha particle but lighter than a typical binary fission fragment Cluster decay (also named heavy particle radioactivity or heavy...  (10−14%)Heaviest known nuclide to undergo cluster decay Cluster decay Cluster decay is a type of nuclear decay in which a parent atomic nucleus with A nucleons and Z protons emits a cluster of Ne neutrons and Ze protons heavier than an alpha particle but lighter than a typical binary fission fragment Cluster decay (also named heavy particle radioactivity or heavy...	208Pb 34Si
					β+β+ (rare)	242Pu
243Cm	96	147	243.0613891(22)	29.1(1) a	α (99.71%)	239Pu	5/2+
					EC (.29%)	243Am
					SF (5.3×10−9%)	(various)
243mCm	87.4(1) keV			1.08(3) µs			1/2+
244Cm	96	148	244.0627526(20)	18.10(2) a	α	240Pu	0+
					SF (1.34×10−4%)	(various)
244mCm	1040.188(12) keV			34(2) ms	IT Isomeric transition An isomeric transition is a radioactive decay process that involves emission of a gamma ray from an atom where the nucleus is in an excited metastable state, referred to in its excited state, as a nuclear isomer....	244Cm	6+
245Cm	96	149	245.0654912(22)	8.5(1)×103 a	α	241Pu	7/2+
					SF (6.1×10−7%)	(various)
245mCm	355.90(10) keV			290(20) ns			1/2+
246Cm	96	150	246.0672237(22)	4.76(4)×103 a	α (99.97%)	242Pu	0+
					SF (.0261%)	(various)
247Cm	96	151	247.070354(5)	1.56(5)×107 a	α	243Pu	9/2-
248Cm	96	152	248.072349(5)	3.48(6)×105 a	α (91.74%)	244Pu	0+
					SF (8.26%)	(various)
					β-β- (rare)	248Cf
249Cm	96	153	249.075953(5)	64.15(3) min	β-	249Bk	1/2(+)
249mCm	48.758(17) keV			23 µs			(7/2+)
250Cm	96	154	250.078357(12)	8,300# a	SF (80%)Lightest nuclide to undergo 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... as the main decay mode	(various)	0+
					α (11%)	246Pu
					β- (9%)	250Bk
251Cm	96	155	251.082285(24)	16.8(2) min	β-	251Bk	(1/2+)
252Cm	96	156	252.08487(32)#	<1 d	β-	252Bk	0+

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.