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{{Distinguish|cerium}}
{{about|the chemical element|the ancient city located in Cyprus|Kourion}}
{{good article}}
{{infobox curium}}
'''Curium''' is a [[synthetic element|synthetic chemical element]]; it has [[Chemical symbol|symbol]] '''Cm''' and [[atomic number]] 96. This [[Transuranium element|transuranic]] [[actinide]] element was named after eminent scientists [[Marie Curie|Marie]] and [[Pierre Curie]], both known for their research on [[radioactivity]]. Curium was first intentionally made by the team of [[Glenn T. Seaborg]], [[Ralph A. James]], and [[Albert Ghiorso]] in 1944, using the [[cyclotron]] at [[Lawrence Berkeley National Laboratory|Berkeley]]. They bombarded the newly discovered element [[plutonium]] (the isotope [[plutonium-239|<sup>239</sup>Pu]]) with [[alpha particle]]s. This was then sent to the [[Metallurgical Laboratory]] at [[University of Chicago]] where a tiny sample of curium was eventually separated and identified. The discovery was kept secret until after the end of [[World War II]]. The news was released to the public in November 1947. Most curium is produced by bombarding [[uranium]] or plutonium with [[neutron]]s in [[nuclear reactor]]s – one [[tonne]] of spent [[nuclear fuel]] contains ~20 grams of curium. 

Curium is a hard, dense, silvery metal with a high melting and boiling point for an actinide. It is [[paramagnetism|paramagnetic]] at [[Standard temperature and pressure|ambient conditions]], but becomes [[antiferromagnetism|antiferromagnetic]] upon cooling, and other magnetic transitions are also seen in many curium compounds. In compounds, curium usually has [[valence (chemistry)|valence]] +3 and sometimes +4; the +3 valence is predominant in solutions. Curium readily oxidizes, and its oxides are a dominant form of this element. It forms strongly [[fluorescence|fluorescent]] complexes with various organic compounds. If it gets into the human body, curium accumulates in bones, lungs, and liver, where it promotes [[cancer]].

All known [[isotope]]s of curium are radioactive and have small [[critical mass]] for a [[nuclear chain reaction]]. The most stable isotope, <sup>247</sup>Cm, has a half-life of 15.6&nbsp;million years; the longest-lived curium isotopes predominantly emit [[alpha decay|alpha particles]]. [[Radioisotope thermoelectric generator]]s can use the heat from this process, but this is hindered by the rarity and high cost of curium. Curium is used in making heavier actinides and the <sup>238</sup>Pu [[radionuclide]] for power sources in [[artificial cardiac pacemaker]]s and [[radioisotope thermoelectric generator|RTG]]s for spacecraft. It served as the α-source in the [[alpha particle X-ray spectrometer]]s of several space probes, including the ''[[Sojourner (rover)|Sojourner]]'', ''[[Spirit (rover)|Spirit]]'', ''[[Opportunity (rover)|Opportunity]]'', and ''[[Curiosity (rover)|Curiosity]]'' [[Mars rover]]s and the [[Philae (spacecraft)|Philae lander]] on [[comet]] [[67P/Churyumov–Gerasimenko]], to analyze the composition and structure of the surface.

==History==
[[File:Glenn Seaborg - 1964.jpg|thumb|left|upright|[[Glenn T. Seaborg]]]]
[[File:Berkeley 60-inch cyclotron.jpg|thumb|left|upright|The {{convert|60|in|cm|adj=on}} cyclotron at the Lawrence Radiation Laboratory, University of California, Berkeley, in August 1939.]]
Though curium had likely been produced in previous nuclear experiments as well as the [[natural nuclear fission reactor]] at Oklo, Gabon, it was [[timeline of chemical element discoveries|first intentionally synthesized]], isolated and identified in 1944, at [[University of California, Berkeley]], by [[Glenn T. Seaborg]], [[Ralph A. James]], and [[Albert Ghiorso]]. In their experiments, they used a {{convert|60|in|cm|adj=on}} [[cyclotron]].<ref>{{cite book|title = The New Chemistry: A Showcase for Modern Chemistry and Its Applications|first = Nina|last = Hall|publisher = Cambridge University Press|date = 2000|pages = [https://archive.org/details/newchemistry00hall/page/8 8]–9|isbn = 978-0-521-45224-3|url = https://archive.org/details/newchemistry00hall|url-access = registration}}</ref>

Curium was chemically identified at the Metallurgical Laboratory (now [[Argonne National Laboratory]]), [[University of Chicago]]. It was the third [[transuranium element]] to be discovered even though it is the fourth in the series – the lighter element [[americium]] was still unknown.<ref name="E96">{{cite journal|last1=Seaborg|first1=Glenn T. |last2=James |first2=R. A. |last3=Ghiorso|first3=A.|title=The New Element Curium (Atomic Number 96)|journal=NNES PPR (National Nuclear Energy Series, Plutonium Project Record)|volume=14 B|series=The Transuranium Elements: Research Papers, Paper No.&nbsp;22.2 |year=1949|osti=4421946|url=http://www.osti.gov/accomplishments/documents/fullText/ACC0049.pdf|archive-url=https://web.archive.org/web/20071012083344/http://www.osti.gov/accomplishments/documents/fullText/ACC0049.pdf|archive-date=12 October 2007}}</ref><ref name="Morrs" />

The sample was prepared as follows: first [[plutonium]] nitrate solution was coated on a [[platinum]] foil of ~0.5&nbsp;cm<sup>2</sup> area, the solution was evaporated and the residue was converted into [[plutonium(IV) oxide]] (PuO<sub>2</sub>) by [[annealing (materials science)|annealing]]. Following cyclotron irradiation of the oxide, the coating was dissolved with [[nitric acid]] and then precipitated as the hydroxide using concentrated aqueous [[ammonia solution]]. The residue was dissolved in [[perchloric acid]], and further separation was done by [[ion exchange]] to yield a certain isotope of curium. The separation of curium and americium was so painstaking that the Berkeley group initially called those elements ''[[wikt:pandemonium|pandemonium]]'' (from Greek for ''all demons'' or ''hell'') and ''[[wikt:delirium|delirium]]'' (from Latin for ''madness'').<ref name="radio" /><ref>Krebs, Robert E. [https://books.google.com/books?id=yb9xTj72vNAC&pg=PA322 The history and use of our earth's chemical elements: a reference guide], Greenwood Publishing Group, 2006, {{ISBN|0-313-33438-2}} p. 322</ref>

Curium-242 was made in July–August 1944 by bombarding <sup>239</sup>Pu with [[alpha decay|α-particles]] to produce curium with the release of a [[neutron]]:<ref name="E96"/><ref>{{Cite web |title=Curium {{!}} Radioactive, Synthetic, Actinide {{!}} Britannica |url=https://www.britannica.com/science/curium-chemical-element |access-date=2025-02-15 |website=www.britannica.com |language=en}}</ref>
: <chem>^{239}_{94}Pu + ^{4}_{2}He -> ^{242}_{96}Cm + ^{1}_{0}n</chem>

Curium-242 was unambiguously identified by the characteristic energy of the α-particles emitted during the decay:
: <chem>^{242}_{96}Cm -> ^{238}_{94}Pu + ^{4}_{2}He</chem>
The [[half-life]] of this [[alpha decay]] was first measured as 5 months (150 days)<ref name="E96"/> and then corrected to 162.8 days.{{NUBASE2020|name}}

Another isotope <sup>240</sup>Cm was produced in a similar reaction in March 1945:
: <chem>^{239}_{94}Pu + ^{4}_{2}He -> ^{240}_{96}Cm + 3^{1}_{0}n</chem>
The α-decay half-life of <sup>240</sup>Cm was determined as 26.8 days<ref name="E96"/> and later revised to 30.4 days.{{NUBASE2020|name}}

The discovery of curium and americium in 1944 was closely related to the [[Manhattan Project]], so the results were confidential and declassified only in 1945. Seaborg leaked the synthesis of the elements 95 and 96 on the U.S. radio show for children, the ''[[Quiz Kids]]'', five days before the official presentation at an [[American Chemical Society]] meeting on November 11, 1945, when one listener asked if any new transuranic element beside plutonium and [[neptunium]] had been discovered during the war.<ref name="radio">{{cite web|url = http://pubs.acs.org/cen/80th/americium.html|title = Chemical & Engineering News: It's Elemental: The Periodic Table – Americium|access-date = 2008-12-07| first = Rachel Sheremeta|last = Pepling|date = 2003}}</ref> The discovery of curium (<sup>242</sup>Cm and <sup>240</sup>Cm), its production, and its compounds was later patented listing only Seaborg as the inventor.<ref>Seaborg, G. T. {{US patent|3161462}} "Element", Filing date: 7 February 1949, Issue date: December 1964</ref>

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The element was named after [[Marie Curie]] and her husband [[Pierre Curie]], who are known for discovering [[radium]] and for their work in [[radioactivity]]. It followed the example of [[gadolinium]], a [[lanthanide]] element above curium in the periodic table, which was named after the explorer of [[rare-earth element]]s [[Johan Gadolin]]:<ref>Greenwood, p. 1252</ref>
::<blockquote>As the name for the element of atomic number 96 we should like to propose "curium", with symbol Cm. The evidence indicates that element 96 contains seven 5f electrons and is thus analogous to the element gadolinium, with its seven 4f electrons in the regular rare earth series. On this basis element 96 is named after the Curies in a manner analogous to the naming of gadolinium, in which the chemist Gadolin was honored.<ref name="E96" /></blockquote>

The first curium samples were barely visible, and were identified by their radioactivity. Louis Werner and [[Isadore Perlman]] made the first substantial sample of 30&nbsp;μg curium-242 hydroxide at University of California, Berkeley in 1947 by bombarding [[americium]]-241 with neutrons.<ref name="CRC">Hammond C. R. "The elements" in {{RubberBible86th}}</ref><ref>L. B. Werner, I. Perlman: "Isolation of Curium", NNES PPR (''National Nuclear Energy Series, Plutonium Project Record''), Vol.&nbsp;14&nbsp;B, ''The Transuranium Elements: Research Papers'', Paper No.&nbsp;22.5, McGraw-Hill Book Co., Inc., New York, 1949.</ref><ref>{{cite web|url=http://www.nap.edu/readingroom.php?book=biomems&page=iperlman.html |title=National Academy of Sciences. Isadore Perlman 1915–1991 |publisher=Nap.edu |access-date=2011-03-25}}</ref> Macroscopic amounts of [[curium(III) fluoride]] were obtained in 1950 by W. W. T. Crane, J. C. Wallmann and B. B. Cunningham. Its magnetic susceptibility was very close to that of GdF<sub>3</sub> providing the first experimental evidence for the +3 valence of curium in its compounds.<ref name="CRC" /> Curium metal was produced only in 1950 by reduction of CmF<sub>3</sub> with [[barium]].<ref name="CM_METALL">{{cite journal|first1 = J. C.|last1 = Wallmann|first2 = W. W. T.|last2 = Crane|first3 = B. B.|last3 = Cunningham|title = The Preparation and Some Properties of Curium Metal|journal = [[Journal of the American Chemical Society]]|date = 1951|volume =73|issue =1|pages = 493–494|doi = 10.1021/ja01145a537|hdl = 2027/mdp.39015086479790|url = https://cloudfront.escholarship.org/dist/prd/content/qt51t3d12j/qt51t3d12j.pdf}}</ref><ref>{{cite journal|author =Werner, L. B.|author2 =Perlman, I.|title =First Isolation of Curium| journal = Journal of the American Chemical Society|date = 1951| volume =73|issue =1|pages = 5215–5217|doi = 10.1021/ja01155a063|s2cid =95799539}}</ref>

==Characteristics==

===Physical===
[[File:Closest packing ABAC.png|thumb|Double-hexagonal close packing with the layer sequence ABAC in the crystal structure of α-curium (A: green, B: blue, C: red)]]
[[File:Cm(HDPA)3·H2O_PL_420_nm.jpg|220x124px|thumb|right|[[Photoluminescence]] of the Cm(HDPA)<sub>3</sub>·H<sub>2</sub>O crystal upon [[irradiation]] with 420&nbsp;nm light]]
A synthetic, radioactive element, curium is a hard, dense metal with a silvery-white appearance and physical and chemical properties resembling [[gadolinium]]. Its melting point of 1344&nbsp;°C is significantly higher than that of the previous elements neptunium (637&nbsp;°C), plutonium (639&nbsp;°C) and americium (1176&nbsp;°C). In comparison, gadolinium melts at 1312&nbsp;°C. Curium boils at 3556&nbsp;°C. With a density of 13.52&nbsp;g/cm<sup>3</sup>, curium is lighter than neptunium (20.45&nbsp;g/cm<sup>3</sup>) and plutonium (19.8&nbsp;g/cm<sup>3</sup>), but heavier than most other metals. Of two crystalline forms of curium, α-Cm is more stable at ambient conditions. It has a hexagonal symmetry, [[space group]] P6<sub>3</sub>/mmc, lattice parameters ''a''&nbsp;=&nbsp;365&nbsp;[[picometer|pm]] and ''c''&nbsp;=&nbsp;1182&nbsp;pm, and four [[formula unit]]s per [[unit cell]].<ref name="Milman">{{cite journal|last1=Milman|first1=V.|title=Crystal structures of curium compounds: an ab initio study|journal=Journal of Nuclear Materials|volume=322|issue=2–3|page=165|date=2003|doi=10.1016/S0022-3115(03)00321-0|bibcode=2003JNuM..322..165M|last2=Winkler|first2=B.|last3=Pickard|first3=C. J.}}</ref> The crystal consists of double-[[Close-packing of equal spheres|hexagonal close packing]] with the layer sequence ABAC and so is isotypic with α-lanthanum. At pressure >23&nbsp;[[Pascal (unit)|GPa]], at room temperature, α-Cm becomes β-Cm, which has [[Cubic crystal system|face-centered cubic]] symmetry, space group Fm{{overline|3}}m and lattice constant ''a''&nbsp;=&nbsp;493&nbsp;pm.<ref name = "Milman" /> On further compression to 43&nbsp;GPa, curium becomes an [[Orthorhombic crystal system|orthorhombic]] γ-Cm structure similar to α-uranium, with no further transitions observed up to 52&nbsp;GPa. These three curium phases are also called Cm I, II and III.<ref>Young, D. A. [https://books.google.com/books?id=F2HVYh6wLBcC&pg=PA227 Phase diagrams of the elements], University of California Press, 1991, {{ISBN|0-520-07483-1}}, p. 227</ref><ref>{{cite journal|last1=Haire|first1=R.|last2=Peterson|first2=J.|last3=Benedict|first3=U.|last4=Dufour|first4=C.|last5=Itie|first5=J.|title=X-ray diffraction of curium-248 metal under pressures of up to 52 GPa|journal=Journal of the Less Common Metals|volume=109|issue=1|page=71|date=1985|doi=10.1016/0022-5088(85)90108-0}}</ref>

Curium has peculiar magnetic properties. Its neighbor element americium shows no deviation from [[Curie–Weiss law|Curie-Weiss]] [[paramagnetism]] in the entire temperature range, but α-Cm transforms to an [[Antiferromagnetism|antiferromagnetic]] state upon cooling to 65–52&nbsp;K,<ref>{{cite journal|last1=Kanellakopulos|first1=B.|title=The magnetic susceptibility of Americium and curium metal|journal=Solid State Communications|volume=17|issue=6|page=713|date=1975|doi=10.1016/0038-1098(75)90392-0|bibcode = 1975SSCom..17..713K|last2=Blaise|first2=A.|last3=Fournier|first3=J. M.|last4=Müller|first4=W. }}</ref><ref>{{cite journal|last1=Fournier|first1=J.|title=Curium: A new magnetic element|journal=Physica B+C|volume=86–88|page=30|date=1977|doi=10.1016/0378-4363(77)90214-5|bibcode = 1977PhyBC..86...30F|last2=Blaise|first2=A.|last3=Muller|first3=W.|last4=Spirlet|first4=J.-C. }}</ref> and β-Cm exhibits a [[Ferrimagnetism|ferrimagnetic]] transition at ~205&nbsp;K. Curium pnictides show [[Ferromagnetism|ferromagnetic]] transitions upon cooling: <sup>244</sup>CmN and <sup>244</sup>CmAs at 109&nbsp;K, <sup>248</sup>CmP at 73&nbsp;K and <sup>248</sup>CmSb at 162&nbsp;K. The lanthanide analog of curium, gadolinium, and its pnictides, also show magnetic transitions upon cooling, but the transition character is somewhat different: Gd and GdN become ferromagnetic, and GdP, GdAs and GdSb show antiferromagnetic ordering.<ref>Nave, S. E.; Huray, P. G.; Peterson, J. R. and Damien, D. A. [http://www.osti.gov/bridge/purl.cover.jsp;jsessionid=ECF73C70531D64E8B663048ECE8C10F9?purl=/6263633-jkoGGI/ Magnetic susceptibility of curium pnictides], Oak Ridge National Laboratory</ref>

In accordance with magnetic data, electrical resistivity of curium increases with temperature – about twice between 4 and 60&nbsp;K – and then is nearly constant up to room temperature. There is a significant increase in resistivity over time (~{{val|10|u=μΩ·cm/h}}) due to self-damage of the crystal lattice by alpha decay. This makes uncertain the true resistivity of curium (~{{val|125|u=μΩ·cm}}). Curium's resistivity is similar to that of gadolinium, and the actinides plutonium and neptunium, but significantly higher than that of americium, uranium, [[polonium]] and [[thorium]].<ref name="res" />

Under ultraviolet illumination, curium(III) ions show strong and stable yellow-orange [[fluorescence]] with a maximum in the range of 590–640&nbsp;nm depending on their environment.<ref name="denecke">{{cite journal|last1=Denecke|first1=Melissa A.|last2=Rossberg|first2=André|last3=Panak|first3=Petra J.|last4=Weigl|first4=Michael|last5=Schimmelpfennig|first5=Bernd|last6=Geist|first6=Andreas|title=Characterization and Comparison of Cm(III) and Eu(III) Complexed with 2,6-Di(5,6-dipropyl-1,2,4-triazin-3-yl)pyridine Using EXAFS, TRFLS, and Quantum-Chemical Methods|journal=Inorganic Chemistry|volume=44|issue=23|date=2005|pmid=16270980|doi=10.1021/ic0511726|pages=8418–8425}}</ref> The fluorescence originates from the transitions from the first excited state <sup>6</sup>D<sub>7/2</sub> and the ground state <sup>8</sup>S<sub>7/2</sub>. Analysis of this fluorescence allows monitoring interactions between Cm(III) ions in organic and inorganic complexes.<ref name="plb">Bünzli, J.-C. G. and Choppin, G. R. ''Lanthanide probes in life, chemical, and earth sciences: theory and practice'', Elsevier, Amsterdam, 1989 {{ISBN|0-444-88199-9}}</ref>

===Chemical===
[[File:Curium-248.png|thumb|A solution of curium|right|150px]]
Curium ion in solution almost always has a +3 [[oxidation state]], the most stable oxidation state for curium.<ref>Penneman, p. 24</ref> A +4 oxidation state is seen mainly in a few solid phases, such as CmO<sub>2</sub> and CmF<sub>4</sub>.<ref>{{cite journal|last1=Keenan|first1=Thomas K.|title=First Observation of Aqueous Tetravalent Curium|journal=Journal of the American Chemical Society|volume=83|issue=17|page=3719|date=1961|doi=10.1021/ja01478a039}}</ref><ref name = "asprey" /> Aqueous curium(IV) is only known in the presence of strong oxidizers such as [[potassium persulfate]], and is easily reduced to curium(III) by [[radiolysis]] and even by water itself.<ref name="Lumetta" /> Chemical behavior of curium is different from the actinides thorium and uranium, and is similar to americium and many [[lanthanide]]s. In aqueous solution, the Cm<sup>3+</sup> ion is colorless to pale green;<ref name="g1265">Greenwood, p. 1265</ref> Cm<sup>4+</sup> ion is pale yellow.<ref name="HOWI_1956">Holleman, p. 1956</ref> The optical absorption of Cm<sup>3+</sup> ion contains three sharp peaks at 375.4, 381.2 and 396.5&nbsp;nm and their strength can be directly converted into the concentration of the ions.<ref>Penneman, pp. 25–26</ref> The +6 oxidation state has only been reported once in solution in 1978, as the curyl ion ({{chem|CmO|2|2+}}): this was prepared from [[beta decay]] of [[americium-242]] in the americium(V) ion {{chem|242|AmO|2|+}}.<ref name="CmO3" /> Failure to get Cm(VI) from oxidation of Cm(III) and Cm(IV) may be due to the high Cm<sup>4+</sup>/Cm<sup>3+</sup> [[ionization energy|ionization potential]] and the instability of Cm(V).<ref name="Lumetta">{{cite book|first1 = Lumetta|last1 = Gregg J.|first2 = Major C.|last2 = Thompson|first3 = Robert A.|last3 = Penneman|first4 = P. Gary|last4 = Eller|contribution = Curium|title = The Chemistry of the Actinide and Transactinide Elements|editor1-first = Lester R.|editor1-last = Morss|editor2-first = Norman M.|editor2-last = Edelstein|editor3-first = Jean|editor3-last = Fuger|edition = 3rd|date = 2006|volume = 3|publisher = Springer|location = Dordrecht, the Netherlands|pages = 1397–1443|url = http://radchem.nevada.edu/classes/rdch710/files/neptunium.pdf|doi = 10.1007/1-4020-3598-5_9|isbn = 978-1-4020-3555-5|access-date = 2013-10-18|archive-date = 2018-01-17|archive-url = https://web.archive.org/web/20180117190715/http://radchem.nevada.edu/classes/rdch710/files/neptunium.pdf|url-status = dead}}</ref>

Curium ions are [[HSAB theory|hard Lewis acids]] and thus form most stable complexes with hard bases.<ref>{{cite journal|last1=Jensen|first1=Mark P.|last2=Bond|first2=Andrew H.|title=Comparison of Covalency in the Complexes of Trivalent Actinide and Lanthanide Cations|journal=Journal of the American Chemical Society|volume=124|issue=33|date=2002|pmid=12175247|doi=10.1021/ja0178620|pages=9870–9877|url=https://figshare.com/articles/Comparison_of_Covalency_in_the_Complexes_of_Trivalent_Actinide_and_Lanthanide_Cations/3640428}}</ref> The bonding is mostly ionic, with a small covalent component.<ref>{{cite journal|last1=Seaborg |first1=Glenn T. |title=Overview of the Actinide and Lanthanide (the ''f'') Elements|journal=Radiochimica Acta|date=1993|volume=61|issue=3–4 |pages=115–122|doi=10.1524/ract.1993.61.34.115 |s2cid=99634366 }}</ref> Curium in its complexes commonly exhibits a 9-fold coordination environment, with a [[tricapped trigonal prismatic molecular geometry]].<ref>Greenwood, p. 1267</ref>

===Isotopes===
{{see also|Isotopes of curium}}
About 19 [[radioisotope]]s and 7 [[nuclear isomer]]s, <sup>233</sup>Cm to <sup>251</sup>Cm, are known; none are [[stable isotope|stable]]. The longest half-lives are 15.6 million years (<sup>247</sup>Cm) and 348,000 years (<sup>248</sup>Cm). Other long-lived ones are <sup>245</sup>Cm (8500 years), <sup>250</sup>Cm (8300 years) and <sup>246</sup>Cm (4760 years). Curium-250 is unusual: it mostly (~86%) decays by [[spontaneous fission]]. The most commonly used isotopes are <sup>242</sup>Cm and <sup>244</sup>Cm with the half-lives 162.8 days and 18.11 years, respectively.{{NUBASE2020|name}}
<div style="float:right; margin:0.5em; font-size:85%;">
{| class="wikitable"
!colspan="7"| [[Neutron temperature#Thermal|Thermal neutron]] [[Neutron cross section|cross sections]] ([[Barn (unit)|barns]])<ref>Pfennig, G.; Klewe-Nebenius, H. and Seelmann Eggebert, W. (Eds.): Karlsruhe [[nuclide]], 6th Ed. 1998</ref>
|-
| ||<sup>242</sup>Cm||<sup>243</sup>Cm||<sup>244</sup>Cm||<sup>245</sup>Cm||<sup>246</sup>Cm||<sup>247</sup>Cm
|-
|Fission||5||617||1.04||2145||0.14||81.90
|-
|Capture||16||130||15.20||369||1.22||57
|-
|C/F ratio||3.20||0.21||14.62||0.17||8.71||0.70
|-
!colspan="7"| [[Enriched uranium#Low-enriched uranium (LEU)|LEU]] [[spent nuclear fuel]] 20 years after 53 MWd/kg [[burnup]]<ref>{{cite journal|doi=10.1080/08929880500357682|last1=Kang|date=2005|page=169|issue=3|volume=13|journal=Science and Global Security|url=http://www.princeton.edu/sgs/publications/sgs/pdf/13_3%20Kang%20vonhippel.pdf |archive-url=https://web.archive.org/web/20111128070246/http://www.princeton.edu/sgs/publications/sgs/pdf/13_3%20Kang%20vonhippel.pdf |archive-date=2011-11-28 |url-status=live|first1=Jungmin|last2=Von Hippel|first2=Frank|title=Limited Proliferation-Resistance Benefits from Recycling Unseparated Transuranics and Lanthanides from Light-Water Reactor Spent Fuel|bibcode=2005S&GS...13..169K|s2cid=123552796}}</ref>
|-
|colspan="2" |3 common isotopes ||51||3700||390|| ||
|-
!colspan="7"| [[Fast-neutron reactor]] [[MOX fuel]] (avg 5 samples, [[burnup]] 66–120 GWd/t)<ref>{{cite journal|doi=10.3327/jnst.38.912 |title=Analysis of Curium Isotopes in Mixed Oxide Fuel Irradiated in Fast Reactor |journal=Journal of Nuclear Science and Technology |volume=38 |date=2001 |issue=10 |pages=912–914 |author=Osaka, M. |display-authors=etal |doi-access=free }}</ref>
|-
|colspan="2" |Total curium 3.09{{e|-3}}% ||27.64%||70.16%||2.166%||0.0376%||0.000928%
|}
{| Class = "wikitable"
|-
| Isotope||<sup>242</sup>Cm||<sup>243</sup>Cm||<sup>244</sup>Cm||<sup>245</sup>Cm||<sup>246</sup>Cm||<sup>247</sup>Cm||<sup>248</sup>Cm||<sup>250</sup>Cm
|-
|[[Critical mass]], kg|| 25|| 7.5||33||6.8||39||7||40.4||23.5
|}
</div>

All isotopes ranging from <sup>242</sup>Cm to <sup>248</sup>Cm, as well as <sup>250</sup>Cm, undergo a self-sustaining [[nuclear chain reaction]] and thus in principle can be a [[nuclear fuel]] in a reactor. As in most transuranic elements, [[nuclear fission]] cross section is especially high for the odd-mass curium isotopes <sup>243</sup>Cm, <sup>245</sup>Cm and <sup>247</sup>Cm. These can be used in [[thermal-neutron reactor]]s, whereas a mixture of curium isotopes is only suitable for [[Breeder reactor#Fast breeder reactor|fast breeder reactors]] since the even-mass isotopes are not fissile in a thermal reactor and accumulate as burn-up increases.<ref name="irsn">Institut de Radioprotection et de Sûreté Nucléaire: [http://ec.europa.eu/energy/nuclear/transport/doc/irsn_sect03_146.pdf "Evaluation of nuclear criticality safety. data and limits for actinides in transport"] {{webarchive |url=https://web.archive.org/web/20110519171204/http://ec.europa.eu/energy/nuclear/transport/doc/irsn_sect03_146.pdf |date=May 19, 2011 }}, p. 16</ref> The mixed-oxide (MOX) fuel, which is to be used in power reactors, should contain little or no curium because [[neutron activation]] of <sup>248</sup>Cm will create [[californium]]. Californium is a strong [[neutron]] emitter, and would pollute the back end of the fuel cycle and increase the dose to reactor personnel. Hence, if [[minor actinide]]s are to be used as fuel in a thermal neutron reactor, the curium should be excluded from the fuel or placed in special fuel rods where it is the only actinide present.<ref>{{cite book|author=National Research Council (U.S.). Committee on Separations Technology and Transmutation Systems|title=Nuclear wastes: technologies for separations and transmutation|url=https://books.google.com/books?id=iRI7Cx2D4e4C&pg=PA231|access-date=19 April 2011|date=1996|publisher=National Academies Press|isbn=978-0-309-05226-9|pages=231–}}</ref>

[[File:Sasahara.svg|thumb|upright=1.5|Transmutation flow between <sup>238</sup>Pu and <sup>244</sup>Cm in LWR.<ref>{{cite journal|url=http://nuclear.ee.duth.gr/upload/A11%20%20%20200401.pdf |archive-url=https://web.archive.org/web/20150903170300/http://nuclear.ee.duth.gr/upload/A11%20%20%20200401.pdf |archive-date=2015-09-03 |url-status=live|title=Neutron and Gamma Ray Source Evaluation of LWR High Burn-up UO2 and MOX Spent Fuels|journal=Journal of Nuclear Science and Technology|volume=41|issue=4|pages=448–456|date=2004|doi=10.3327/jnst.41.448|author=Sasahara, Akihiro|last2=Matsumura|first2=Tetsuo|last3=Nicolaou|first3=Giorgos|last4=Papaioannou|first4=Dimitri|doi-access=free}}</ref><br />Fission percentage is 100 minus shown percentages.<br />Total rate of transmutation varies greatly by nuclide.<br /><sup>245</sup>Cm–<sup>248</sup>Cm are long-lived with negligible decay.]]
The adjacent table lists the [[critical mass]]es for curium isotopes for a sphere, without moderator or reflector. With a metal reflector (30&nbsp;cm of steel), the critical masses of the odd isotopes are about 3–4&nbsp;kg. When using water (thickness ~20–30&nbsp;cm) as the reflector, the critical mass can be as small as 59&nbsp;grams for <sup>245</sup>Cm, 155&nbsp;grams for <sup>243</sup>Cm and 1550&nbsp;grams for <sup>247</sup>Cm. There is significant uncertainty in these critical mass values. While it is usually on the order of 20%, the values for <sup>242</sup>Cm and <sup>246</sup>Cm were listed as large as 371&nbsp;kg and 70.1&nbsp;kg, respectively, by some research groups.<ref name="irsn" /><ref>{{cite journal|author=Okundo, H.|author2=Kawasaki, H.|name-list-style=amp |title=Critical and Subcritical Mass Calculations of Curium-243 to −247 Based on JENDL-3.2 for Revision of ANSI/ANS-8.15|journal=Journal of Nuclear Science and Technology|date=2002|volume=39|pages=1072–1085|doi=10.3327/jnst.39.1072|issue=10|doi-access=free}}</ref>

Curium is not currently used as nuclear fuel due to its low availability and high price.<ref>[http://bundesrecht.juris.de/atg/__2.html § 2 Begriffsbestimmungen (Atomic Energy Act)] (in German)</ref> <sup>245</sup>Cm and <sup>247</sup>Cm have very small critical mass and so could be used in [[tactical nuclear weapon]]s, but none are known to have been made. Curium-243 is not suitable for such, due to its short half-life and strong α emission, which would cause excessive heat.<ref>{{cite book|author1=Jukka Lehto|author2=Xiaolin Hou|title=Chemistry and Analysis of Radionuclides: Laboratory Techniques and Methodology|url=https://books.google.com/books?id=v2iRJaO3SMIC&pg=PA303|access-date=19 April 2011|date=2 February 2011|publisher=Wiley-VCH|isbn=978-3-527-32658-7|pages=303–}}</ref> Curium-247 would be highly suitable due to its long half-life, which is 647 times longer than [[plutonium-239]] (used in many existing [[nuclear weapon]]s).

===Occurrence===
[[File:Ivy Mike - mushroom cloud.jpg|thumb|Several isotopes of curium were detected in the fallout from the ''[[Ivy Mike]]'' nuclear test.]]
The longest-lived isotope, <sup>247</sup>Cm, has half-life 15.6&nbsp;million years; so any [[primordial nuclide|primordial]] curium, that is, present on Earth when it formed, should have decayed by now. Its past presence as an [[extinct radionuclide]] is detectable as an excess of its primordial, long-lived daughter <sup>235</sup>U.<ref>{{cite news |url=https://phys.org/news/2016-03-cosmochemists-evidence-unstable-heavy-element.html |title=Cosmochemists find evidence for unstable heavy element at solar system formation |date=2016 |publisher=University of Chicago |website=phys.org |access-date=6 June 2022}}</ref> Traces of <sup>242</sup>Cm may occur naturally in uranium minerals due to neutron capture and beta decay (<sup>238</sup>U → <sup>239</sup>Pu → <sup>240</sup>Pu → <sup>241</sup>Am → <sup>242</sup>Cm), though the quantities would be tiny and this has not been confirmed: even with "extremely generous" estimates for neutron absorption possibilities, the quantity of <sup>242</sup>Cm present in 1&nbsp;×&nbsp;10<sup>8</sup>&nbsp;kg of 18% uranium pitchblende would not even be one atom.<ref name=ThorntonBurdette/><ref>{{Cite web|url=https://www.livescience.com/39915-facts-about-curium.html|title=Facts About Curium|last=Earth|first=Live Science Staff 2013-09-24T21:44:13Z Planet|website=livescience.com|date=24 September 2013|language=en|access-date=2019-08-10}}</ref><ref>{{Cite web|url=http://www.rsc.org/periodic-table/element/96/curium|title=Curium - Element information, properties and uses {{!}} Periodic Table|website=www.rsc.org|access-date=2019-08-10}}</ref> Traces of <sup>247</sup>Cm are also probably brought to Earth in [[cosmic ray]]s, but this also has not been confirmed.<ref name=ThorntonBurdette>{{cite journal |last1=Thornton |first1=Brett F. |last2=Burdette |first2=Shawn C. |date=2019 |title=Neutron stardust and the elements of Earth |url=https://www.nature.com/articles/s41557-018-0190-9 |journal=Nature Chemistry |volume=11 |issue=1 |pages=4–10 |doi=10.1038/s41557-018-0190-9 |pmid=30552435 |bibcode=2019NatCh..11....4T |s2cid=54632815 |access-date=19 February 2022}}</ref> There is also the possibility of <sup>244</sup>Cm being produced as the [[double beta decay]] daughter of natural <sup>244</sup>Pu.<ref name=ThorntonBurdette/><ref name="Tretyak2002">{{Cite journal
 |last1=Tretyak |first1=V.I. 
 |last2=Zdesenko |first2=Yu.G. 
 |year=2002
 |title=Tables of Double Beta Decay Data — An Update
 |journal=[[At. Data Nucl. Data Tables]] |volume=80 |issue=1 |pages=83–116
 |doi=10.1006/adnd.2001.0873
|bibcode=2002ADNDT..80...83T }}</ref>

Curium is made artificially in small amounts for research purposes. It also occurs as one of the waste products in [[spent nuclear fuel]].<ref>{{cite journal |vauthors = Chaplin J, Warwick P, Cundy A, Bochud F, Froidevaux P |title=Novel DGT Configurations for the Assessment of Bioavailable Plutonium, Americium, and Uranium in Marine and Freshwater Environments |journal=Analytical Chemistry |date=25 August 2021 |volume=93 |issue=35 |pages=11937–11945 |doi=10.1021/acs.analchem.1c01342 |pmid=34432435 |s2cid=237307309 |doi-access=free }}</ref><ref>{{cite journal |vauthors = Chaplin J, Christl M, Straub M, Bochud F, Froidevaux P |title=Passive Sampling Tool for Actinides in Spent Nuclear Fuel Pools |journal=ACS Omega |date=2 June 2022 |volume=7 |issue=23 |pages=20053−20058 |doi=10.1021/acsomega.2c01884 |pmid=35722008 |pmc=9202248 |hdl=20.500.11850/554631 |url=https://doi.org/10.1021/acsomega.2c01884}}</ref> Curium is present in nature in some areas used for [[nuclear weapons testing]].<ref name="lenntech">[http://www.lenntech.de/pse/pse.htm Curium] (in German)</ref> Analysis of the debris at the test site of the [[United States]]' first [[thermonuclear weapon]], [[Ivy Mike]] (1 November 1952, [[Enewetak Atoll]]), besides [[einsteinium]], [[fermium]], [[plutonium]] and [[americium]] also revealed isotopes of berkelium, californium and curium, in particular <sup>245</sup>Cm, <sup>246</sup>Cm and smaller quantities of <sup>247</sup>Cm, <sup>248</sup>Cm and <sup>249</sup>Cm.<ref>{{cite journal|last1=Fields|first1=P. R.|last2=Studier|first2=M. H.|last3=Diamond|first3=H.|last4=Mech|first4=J. F.|last5=Inghram|first5=M. G.|last6=Pyle|first6=G. L.|last7=Stevens|first7=C. M.|last8=Fried|first8=S.|last9=Manning|first9=W. M.|last10=Ghiorso|first10=A.|last11=Thompson|first11=S. G.|last12=Higgins|first12=G. H.|last13=Seaborg|first13=Glenn T.|display-authors=3|title=Transplutonium Elements in Thermonuclear Test Debris|date=1956|journal=Physical Review|volume=102|issue=1|pages=180–182|doi=10.1103/PhysRev.102.180|bibcode=1956PhRv..102..180F}}</ref>

Atmospheric curium compounds are poorly soluble in common solvents and mostly adhere to soil particles. Soil analysis revealed about 4,000 times higher concentration of curium at the sandy soil particles than in water present in the soil pores. An even higher ratio of about 18,000 was measured in [[loam]] soils.<ref name="LA2" />

The [[transuranium element]]s from americium to fermium, including curium, occurred naturally in the [[natural nuclear fission reactor]] at [[Oklo]], but no longer do so.<ref name="emsley">{{cite book|last=Emsley|first=John|title=Nature's Building Blocks: An A-Z Guide to the Elements|edition=New|date=2011|publisher=Oxford University Press|location=New York, NY|isbn=978-0-19-960563-7}}</ref>

Curium, and other non-primordial actinides, have also been suspected to exist in the spectrum of [[Przybylski's Star]].<ref name=gopka08>{{cite journal |last1=Gopka |first1=V. F. |last2=Yushchenko |first2=A. V. |last3=Yushchenko |first3=V. A. |last4=Panov |first4=I. V. |last5=Kim |first5=Ch. |title=Identification of absorption lines of short half-life actinides in the spectrum of Przybylski's star (HD 101065) |journal=Kinematics and Physics of Celestial Bodies |date=15 May 2008 |volume=24 |issue=2 |pages=89–98 |doi=10.3103/S0884591308020049 |bibcode = 2008KPCB...24...89G |s2cid=120526363 }}</ref>

==Synthesis==
===Isotope preparation===
Curium is made in small amounts in [[nuclear reactor]]s, and by now only kilograms of <sup>242</sup>Cm and <sup>244</sup>Cm have been accumulated, and grams or even milligrams for heavier isotopes. Hence the high price of curium, which has been quoted at 160–185 [[United States dollar|USD]] per milligram,<ref name="CRC" /> with a more recent estimate at US$2,000/g for <sup>242</sup>Cm and US$170/g for <sup>244</sup>Cm.<ref name="lect" /> In nuclear reactors, curium is formed from <sup>238</sup>U in a series of nuclear reactions. In the first chain, <sup>238</sup>U captures a neutron and converts into <sup>239</sup>U, which via [[beta decay|β<sup>−</sup> decay]] transforms into <sup>239</sup>Np and <sup>239</sup>Pu.

{{NumBlk|:|<chem>^{238}_{92}U->[\ce{(n,\gamma)}] {^{239}_{92}U} ->[\beta^-][23.5\ \ce{min}] ^{239}_{93}Np ->[\beta^-][2.3565\ \ce{d}] ^{239}_{94}Pu</chem> <small>(the times are [[half-life|half-lives]])</small>.|{{EquationRef|1}}}}

Further neutron capture followed by β<sup>−</sup>-decay gives [[americium]] (<sup>241</sup>Am) which further becomes <sup>242</sup>Cm:
{{NumBlk|:|<chem>^{239}_{94}Pu->[\ce{2(n,\gamma)}] ^{241}_{94}Pu ->[\beta^-][14.35\ \ce{yr}] {^{241}_{95}Am} ->[\ce{(n,\gamma)}] ^{242}_{95}Am ->[\beta^-][16.02 \ce{h}] ^{242}_{96}Cm</chem>.|{{EquationRef|2}}}}

For research purposes, curium is obtained by irradiating not uranium but plutonium, which is available in large amounts from spent nuclear fuel. A much higher neutron flux is used for the irradiation that results in a different reaction chain and formation of <sup>244</sup>Cm:<ref name = "Morrs">Morss, L. R.; Edelstein, N. M. and Fugere, J. (eds): ''The Chemistry of the Actinide Elements and transactinides'', volume 3, Springer-Verlag, Dordrecht 2006, {{ISBN|1-4020-3555-1}}.</ref>
{{NumBlk|:|<chem>^{239}_{94}Pu ->[\ce{4(n,\gamma)}] ^{243}_{94}Pu ->[\beta^-][4.956\ \ce{h}] ^{243}_{95}Am ->[(\ce n,\gamma)] ^{244}_{95}Am ->[\beta^-][10.1 \ce{h}] ^{244}_{96}Cm ->[\alpha][18.11\ \ce{yr}] ^{240}_{94}Pu</chem>|{{EquationRef|3}}}}

Curium-244 alpha decays to <sup>240</sup>Pu, but it also absorbs neutrons, hence a small amount of heavier curium isotopes. Of those, <sup>247</sup>Cm and <sup>248</sup>Cm are popular in scientific research due to their long half-lives. But the production rate of <sup>247</sup>Cm in thermal neutron reactors is low because it is prone to fission due to thermal neutrons.<ref name="haire" /> Synthesis of <sup>250</sup>Cm by [[neutron capture]] is unlikely due to the short half-life of the intermediate <sup>249</sup>Cm (64 min), which β<sup>−</sup> decays to the [[berkelium]] isotope <sup>249</sup>Bk.<ref name="haire" />
<!-- Curium-250 is obtained instead from the α-decay of <sup>254</sup>Cf. For this however, the production rate is low as <sup>254</sup>Cf decays mainly by spontaneous fission, and only slightly by emission of α-particles into <sup>250</sup>Cm.{{Citation needed|date=May 2012}} -->
{{NumBlk|:|<math chem>\ce{^\mathit{A}_{96}Cm{} + ^{1}_{0}n -> ^{\mathit{A}+1}_{96}Cm{} + \gamma} \ (\text{for } 244 \le A \le 248)</math>|{{EquationRef|4}}}}

The above cascade of (n,γ) reactions gives a mix of different curium isotopes. Their post-synthesis separation is cumbersome, so a selective synthesis is desired. Curium-248 is favored for research purposes due to its long half-life. The most efficient way to prepare this isotope is by α-decay of the [[californium]] isotope <sup>252</sup>Cf, which is available in relatively large amounts due to its long half-life (2.65 years). About 35–50&nbsp;mg of <sup>248</sup>Cm is produced thus, per year. The associated reaction produces <sup>248</sup>Cm with isotopic purity of 97%.<ref name="haire">{{cite book
| title = The Chemistry of the Actinide and Transactinide Elements
| editor1-last = Morss
| editor2-first = Norman M.
| editor2-last = Edelstein
| editor3-last = Fuger
| editor3-first = Jean
| last1 = Lumetta
| first1 = Gregg J.
| last2 = Thompson
| first2 = Major C.
| last3 = Penneman
| first3 = Robert A.
| last4 = Eller
| first4 = P. Gary
| chapter = Curium
| chapter-url = http://radchem.nevada.edu/classes/rdch710/files/curium.pdf
| page = 1401
| publisher = [[Springer Science+Business Media]]
| date = 2006
| isbn = 978-1-4020-3555-5
| location = Dordrecht, The Netherlands
| edition = 3rd
| url-status = dead
| archive-url = https://web.archive.org/web/20100717154205/http://radchem.nevada.edu/classes/rdch710/files/curium.pdf
| archive-date = 2010-07-17
}}</ref>

{{NumBlk|:|<math chem>\begin{matrix}{}\\
\ce{^{252}_{98}Cf ->[\alpha][2.645\ \ce{yr}] ^{248}_{96}Cm}\\{}
\end{matrix}</math>|{{EquationRef|5}}}}

Another isotope, <sup>245</sup>Cm, can be obtained for research, from α-decay of <sup>249</sup>Cf; the latter isotope is produced in small amounts from β<sup>−</sup>-decay of <sup>249</sup>[[berkelium|Bk]].
{{NumBlk|:|<chem>
^{249}_{97}Bk ->[\beta^-][330\ \ce{d}] ^{249}_{98}Cf ->[\alpha][351\ \ce{yr}] ^{245}_{96}Cm
</chem>|{{EquationRef|6}}}}

===Metal preparation===
[[File:Elutionskurven Tb Gd Eu und Bk Cm Am.png|thumb|[[Chromatography|Chromatographic]] [[elution]] curves revealing the similarity between Tb, Gd, Eu lanthanides and corresponding Bk, Cm, Am actinides]]
Most synthesis routines yield a mix of actinide isotopes as [[oxide]]s, from which a given isotope of curium needs to be separated. An example procedure could be to dissolve spent reactor fuel (e.g. [[MOX fuel]]) in [[nitric acid]], and remove the bulk of the uranium and plutonium using a [[PUREX]] ('''P'''lutonium – '''UR'''anium '''EX'''traction) type extraction with [[tributyl phosphate]] in a hydrocarbon. The lanthanides and the remaining actinides are then separated from the aqueous residue ([[raffinate]]) by a diamide-based extraction to give, after stripping, a mixture of trivalent actinides and lanthanides. A curium compound is then selectively extracted using multi-step [[chromatography|chromatographic]] and centrifugation techniques with an appropriate reagent.<ref>Penneman, pp. 34–48</ref> [[BTBP|''Bis''-triazinyl bipyridine]] complex has been recently proposed as such reagent which is highly selective to curium.<ref>{{cite journal|author = Magnusson D|author2 = Christiansen B|author3 = Foreman MRS|author4 = Geist A|author5 = Glatz JP|author6 = Malmbeck R|author7 = Modolo G|author8 = Serrano-Purroy D|author9 = Sorel C|name-list-style = amp|journal = Solvent Extraction and Ion Exchange|date = 2009|volume = 27|issue = 2|page = 97|doi = 10.1080/07366290802672204|title = Demonstration of a SANEX Process in Centrifugal Contactors using the CyMe4-BTBP Molecule on a Genuine Fuel Solution|title-link = centrifugal extractor|s2cid = 94720457}}</ref> Separation of curium from the very chemically similar americium can also be done by treating a slurry of their hydroxides in aqueous [[sodium bicarbonate]] with [[ozone]] at elevated temperature. Both americium and curium are present in solutions mostly in the +3 valence state; americium oxidizes to soluble Am(IV) complexes, but curium stays unchanged and so can be isolated by repeated centrifugation.<ref>Penneman, p. 25</ref>

Metallic curium is obtained by [[Redox|reduction]] of its compounds. Initially, curium(III) fluoride was used for this purpose. The reaction was done in an environment free of water and oxygen, in an apparatus made of [[tantalum]] and [[tungsten]], using elemental [[barium]] or [[lithium]] as reducing agents.<ref name="Morrs" /><ref name = "CM_METALL" /><ref name="cunning">{{cite journal|last1=Cunningham|first1=B. B.|last2=Wallmann|first2=J. C.|title=Crystal structure and melting point of curium metal|journal=Journal of Inorganic and Nuclear Chemistry|volume=26|issue=2|page=271|date=1964|doi=10.1016/0022-1902(64)80069-5|osti=4667421}}</ref><ref>{{cite journal|last1=Stevenson|first1=J.|last2=Peterson|first2=J.|title=Preparation and structural studies of elemental curium-248 and the nitrides of curium-248 and berkelium-249|journal=Journal of the Less Common Metals|volume=66|issue=2|page=201|date=1979|doi=10.1016/0022-5088(79)90229-7}}</ref><ref>''Gmelin Handbook of Inorganic Chemistry'', System No. 71, Volume 7 a, transuranics, Part B 1, pp. 67–68.</ref>
:<math>\mathrm{CmF_3\ +\ 3\ Li\ \longrightarrow \ Cm\ +\ 3\ LiF}</math>

Another possibility is reduction of curium(IV) oxide using a magnesium-zinc alloy in a melt of [[magnesium chloride]] and [[magnesium fluoride]].<ref>{{cite journal|last1=Eubanks|first1=I.|title=Preparation of curium metal|journal=Inorganic and Nuclear Chemistry Letters|volume=5|issue=3|page=187|date=1969|doi=10.1016/0020-1650(69)80221-7|last2=Thompson|first2=M. C.}}</ref>

==Compounds and reactions==
{{Main|Curium compounds}}

===Oxides===
Curium readily reacts with oxygen forming mostly Cm<sub>2</sub>O<sub>3</sub> and CmO<sub>2</sub> oxides,<ref name="lenntech" /> but the divalent oxide CmO is also known.<ref name="HOWI_1972">Holleman, p. 1972</ref> Black CmO<sub>2</sub> can be obtained by burning curium [[oxalate]] ({{chem|Cm|2|(C|2|O|4|)|3}}), nitrate ({{chem|Cm|(N|O|3|)|3}}), or hydroxide in pure oxygen.<ref name="asprey" /><ref name="g1268">Greenwood, p. 1268</ref> Upon heating to 600–650&nbsp;°C in vacuum (about 0.01&nbsp;[[Pascal (unit)|Pa]]), it transforms into the whitish Cm<sub>2</sub>O<sub>3</sub>:<ref name="asprey">{{cite journal|last1=Asprey|first1=L. B.|title=Evidence for Quadrivalent Curium: X-Ray Data on Curium Oxides1|last2=Ellinger|first2=F. H.|last3=Fried|first3=S.|last4=Zachariasen|first4=W. H.|journal=Journal of the American Chemical Society|volume=77|issue=6|page=1707|date=1955|doi=10.1021/ja01611a108}}</ref><ref>{{cite journal|last1=Noe|first1=M.|title=Self-radiation effects on the lattice parameter of 244CmO2|journal=Inorganic and Nuclear Chemistry Letters|volume=7|issue=5|page=421|date=1971|doi=10.1016/0020-1650(71)80177-0|last2=Fuger|first2=J.}}</ref>
: <chem>4CmO2 ->[\Delta T] 2Cm2O3 + O2</chem>.

Or, Cm<sub>2</sub>O<sub>3</sub> can be obtained by reducing CmO<sub>2</sub> with molecular [[hydrogen]]:<ref>{{cite journal|last1=Haug|first1=H.|title=Curium sesquioxide Cm2O3|journal=Journal of Inorganic and Nuclear Chemistry|volume=29|issue=11|page=2753|date=1967|doi=10.1016/0022-1902(67)80014-9}}</ref>
: <chem>2CmO2 + H2 -> Cm2O3 + H2O</chem>

Also, a number of ternary oxides of the type M(II)CmO<sub>3</sub> are known, where M stands for a divalent metal, such as barium.<ref>{{cite journal|last1=Fuger|first1=J.|last2=Haire|first2=R.|last3=Peterson|first3=J.|title=Molar enthalpies of formation of BaCmO3 and BaCfO3|journal=Journal of Alloys and Compounds|volume=200|issue=1–2|page=181|date=1993|doi=10.1016/0925-8388(93)90491-5|url=https://zenodo.org/record/1258637}}</ref>

Thermal oxidation of trace quantities of curium hydride (CmH<sub>2–3</sub>) has been reported to give a volatile form of CmO<sub>2</sub> and the volatile trioxide CmO<sub>3</sub>, one of two known examples of the very rare +6 state for curium.<ref name="CmO3" /> Another observed species was reported to behave similar to a supposed plutonium tetroxide and was tentatively characterized as CmO<sub>4</sub>, with curium in the extremely rare +8 state;<ref name="CmO4">{{cite journal |last1=Domanov |first1=V. P. |date=January 2013 |title=Possibility of generation of octavalent curium in the gas phase in the form of volatile tetraoxide CmO<sub>4</sub> |journal=Radiochemistry |volume=55 |issue=1 |pages=46–51 |doi=10.1134/S1066362213010098 |bibcode=2013Radch..55...46D |s2cid=98076989 }}</ref> but new experiments seem to indicate that CmO<sub>4</sub> does not exist, and have cast doubt on the existence of PuO<sub>4</sub> as well.<ref>{{cite journal|last1=Zaitsevskii|first1=Andréi|last2=Schwarz|first2=W. H. Eugen|date=April 2014|title=Structures and stability of AnO4 isomers, An = Pu, Am, and Cm: a relativistic density functional study.|journal=Physical Chemistry Chemical Physics|volume=2014|issue=16|pages=8997–9001|bibcode=2014PCCP...16.8997Z|doi=10.1039/c4cp00235k|pmid=24695756}}<!--|access-date=March 8, 2015--></ref>

===Halides===
The colorless curium(III) fluoride (CmF<sub>3</sub>) can be made by adding fluoride ions into curium(III)-containing solutions. The brown tetravalent curium(IV) fluoride (CmF<sub>4</sub>) on the other hand is only obtained by reacting curium(III) fluoride with molecular [[fluorine]]:<ref name = "Morrs" />
: <math>\mathrm{2\ CmF_3\ +\ F_2\ \longrightarrow\ 2\ CmF_4}</math>

A series of ternary fluorides are known of the form A<sub>7</sub>Cm<sub>6</sub>F<sub>31</sub> (A = [[alkali metal]]).<ref>{{cite journal|last1=Keenan|first1=T.|title=Lattice constants of K7Cm6F31 trends in the 1:1 and 7:6 alkali metal-actinide(IV) series|journal=Inorganic and Nuclear Chemistry Letters|volume=3|issue=10|page=391|date=1967|doi=10.1016/0020-1650(67)80092-8}}</ref>

The colorless [[curium(III) chloride]] (CmCl<sub>3</sub>) is made by reacting [[curium hydroxide]] (Cm(OH)<sub>3</sub>) with anhydrous [[hydrogen chloride]] gas. It can be further turned into other halides such as curium(III) bromide (colorless to light green) and [[curium(III) iodide]] (colorless), by reacting it with the [[ammonia]] salt of the corresponding halide at temperatures of ~400–450&nbsp;°C:<ref>{{cite journal|title=Crystal Structures of the Trifluorides, Trichlorides, Tribromides, and Triiodides of Americium and Curium|last1=Asprey|first1=L. B.|last2=Keenan|first2=T. K.|last3=Kruse|first3=F. H.|journal=Inorganic Chemistry|volume=4|issue=7|page=985|date=1965|doi=10.1021/ic50029a013|s2cid=96551460 |url=https://digital.library.unt.edu/ark:/67531/metadc1035960/}}</ref>
: <math>\mathrm{CmCl_3\ +\ 3\ NH_4I\ \longrightarrow \ CmI_3\ +\ 3\ NH_4Cl}</math>

Or, one can heat curium oxide to ~600°C with the corresponding acid (such as [[hydrobromic acid|hydrobromic]] for curium bromide).<ref>{{cite journal|last1=Burns|first1=J.|title=Crystallographic studies of some transuranic trihalides: 239PuCl3, 244CmBr3, 249BkBr3 and 249CfBr3|journal=Journal of Inorganic and Nuclear Chemistry|volume=37|issue=3|page=743|date=1975|doi=10.1016/0022-1902(75)80532-X|last2=Peterson|first2=J. R.|last3=Stevenson|first3=J. N.}}</ref><ref>{{cite journal|last1=Wallmann|first1=J.|title=Crystal structure and lattice parameters of curium trichloride|journal=Journal of Inorganic and Nuclear Chemistry|volume=29|issue=11|page=2745|date=1967|doi=10.1016/0022-1902(67)80013-7|last2=Fuger|first2=J.|last3=Peterson|first3=J. R.|last4=Green|first4=J. L.|s2cid=97334114 }}</ref> Vapor phase [[hydrolysis]] of curium(III) chloride gives curium oxychloride:<ref>{{cite journal|last1=Weigel|first1=F.|last2=Wishnevsky|first2=V.|last3=Hauske|first3=H.|title=The vapor phase hydrolysis of PuCl3 and CmCl3: heats of formation of PuOC1 and CmOCl|journal=Journal of the Less Common Metals|volume=56|issue=1|page=113|date=1977|doi=10.1016/0022-5088(77)90224-7}}</ref>
: <math>\mathrm{CmCl_3\ +\ \ H_2O\ \longrightarrow \ CmOCl\ +\ 2\ HCl}</math>

===Chalcogenides and pnictides===
Sulfides, selenides and tellurides of curium have been obtained by treating curium with gaseous [[sulfur]], [[selenium]] or [[tellurium]] in vacuum at elevated temperature.<ref>Troc, R. [https://books.google.com/books?id=vkzx_t3zLR0C&pg=PA4 Actinide Monochalcogenides, Volume 27], Springer, 2009 {{ISBN|3-540-29177-6}}, p. 4</ref><ref>{{cite journal|last1=Damien|first1=D.|title=Preparation and lattice parameters of curium sulfides and selenides|journal=Inorganic and Nuclear Chemistry Letters|volume=11|issue=7–8|page=451|date=1975|doi=10.1016/0020-1650(75)80017-1|last2=Charvillat|first2=J. P.|last3=Müller|first3=W.}}</ref> Curium [[pnictogen|pnictides]] of the type CmX are known for [[nitrogen]], [[phosphorus]], [[arsenic]] and [[antimony]].<ref name="Morrs" /> They can be prepared by reacting either curium(III) hydride (CmH<sub>3</sub>) or metallic curium with these elements at elevated temperature.<ref name="CuriumChap9">Lumetta, G. J.; Thompson, M. C.; Penneman, R. A.; Eller, P. G. [http://radchem.nevada.edu/classes/rdch710/files/curium.pdf Curium] {{webarchive|url=https://web.archive.org/web/20100717154205/http://radchem.nevada.edu/classes/rdch710/files/curium.pdf |date=2010-07-17 }}, Chapter Nine in ''Radioanalytical Chemistry'', Springer, 2004, pp. 1420–1421. {{ISBN|0387341226}}, {{ISBN|978-0387 341224}}</ref>

===Organocurium compounds and biological aspects===
[[File:Uranocene-3D-balls.png|thumb|upright=0.5|Predicted curocene structure]]
Organometallic complexes analogous to [[uranocene]] are known also for other actinides, such as thorium, protactinium, neptunium, plutonium and americium. [[Molecular orbital theory]] predicts a stable "curocene" complex (η<sup>8</sup>-C<sub>8</sub>H<sub>8</sub>)<sub>2</sub>Cm, but it has not been reported experimentally yet.<ref>Elschenbroich, Ch. Organometallic Chemistry, 6th edition, Wiesbaden 2008, {{ISBN|978-3-8351-0167-8}}, p. 589</ref><ref>{{cite journal|last1=Kerridge|first1=Andrew|last2=Kaltsoyannis|first2=Nikolas|title=Are the Ground States of the Later Actinocenes Multiconfigurational? All-Electron Spin−Orbit Coupled CASPT2 Calculations on An(η8-C8H8)2(An = Th, U, Pu, Cm)|journal=The Journal of Physical Chemistry A|volume=113|issue=30|date=2009|pmid=19719318|doi=10.1021/jp903912q|pages=8737–8745|bibcode=2009JPCA..113.8737K|url=https://figshare.com/articles/Are_the_Ground_States_of_the_Later_Actinocenes_Multiconfigurational_All_Electron_Spin_Orbit_Coupled_CASPT2_Calculations_on_An_sup_8_sup_C_sub_8_sub_H_sub_8_sub_sub_2_sub_An_Th_U_Pu_Cm_/2840251}}</ref>

Formation of the complexes of the type {{chem|Cm|(|n-C|3|H|7|-BTP)|3}} (BTP = 2,6-di(1,2,4-triazin-3-yl)pyridine), in solutions containing n-C<sub>3</sub>H<sub>7</sub>-BTP and Cm<sup>3+</sup> ions has been confirmed by [[Extended X-ray absorption fine structure|EXAFS]]. Some of these BTP-type complexes selectively interact with curium and thus are useful for separating it from lanthanides and another actinides.<ref name="denecke" /><ref>{{cite journal|last1=Girnt|first1=Denise|last2=Roesky|first2=Peter W.|last3=Geist|first3=Andreas|last4=Ruff|first4=Christian M.|last5=Panak|first5=Petra J.|last6=Denecke|first6=Melissa A.|s2cid=978265|title=6-(3,5-Dimethyl-1H-pyrazol-1-yl)-2,2′-bipyridine as Ligand for Actinide(III)/Lanthanide(III) Separation|journal=Inorganic Chemistry|volume=49|issue=20|date=2010|pmid=20849125|doi=10.1021/ic101309j|pages=9627–9635}}</ref> Dissolved Cm<sup>3+</sup> ions bind with many organic compounds, such as [[hydroxamic acid]],<ref name="pl1">{{cite journal|last1=Glorius|first1=M.|last2=Moll|first2=H.|last3=Bernhard|first3=G.|title=Complexation of curium(III) with hydroxamic acids investigated by time-resolved laser-induced fluorescence spectroscopy|journal=Polyhedron|volume=27|issue=9–10|page=2113|date=2008|doi=10.1016/j.poly.2008.04.002}}</ref> [[urea]],<ref name="pl2">{{cite journal|last1=Heller|first1=Anne|last2=Barkleit|first2=Astrid|last3=Bernhard|first3=Gert|last4=Ackermann|first4=Jörg-Uwe|title=Complexation study of europium(III) and curium(III) with urea in aqueous solution investigated by time-resolved laser-induced fluorescence spectroscopy|journal=Inorganica Chimica Acta|volume=362|issue=4|page=1215|date=2009|doi=10.1016/j.ica.2008.06.016}}</ref> [[fluorescein]]<ref name="pl3">{{cite journal|last1=Moll|first1=Henry|last2=Johnsson|first2=Anna|last3=Schäfer|first3=Mathias|last4=Pedersen|first4=Karsten|last5=Budzikiewicz|first5=Herbert|last6=Bernhard|first6=Gert|title=Curium(III) complexation with pyoverdins secreted by a groundwater strain of Pseudomonas fluorescens|journal=BioMetals|volume=21|issue=2|date=2007|pmid=17653625|doi=10.1007/s10534-007-9111-x|pages=219–228|s2cid=24565144}}</ref> and [[adenosine triphosphate]].<ref name="pl4">{{cite journal|last1=Moll|first1=Henry|last2=Geipel|first2=Gerhard|last3=Bernhard|first3=Gert|title=Complexation of curium(III) by adenosine 5′-triphosphate (ATP): A time-resolved laser-induced fluorescence spectroscopy (TRLFS) study|journal=Inorganica Chimica Acta|volume=358|issue=7|page=2275|date=2005|doi=10.1016/j.ica.2004.12.055}}</ref> Many of these compounds are related to biological activity of various [[microorganism]]s. The resulting complexes show strong yellow-orange emission under UV light excitation, which is convenient not only for their detection, but also for studying interactions between the Cm<sup>3+</sup> ion and the ligands via changes in the half-life (of the order ~0.1 ms) and spectrum of the fluorescence.<ref name="plb" /><ref name="pl1" /><ref name="pl2" /><ref name="pl3" /><ref name="pl4" />

There are a few reports on [[biosorption]] of Cm<sup>3+</sup> by [[bacteria]] and [[archaea]],<ref>{{cite journal|doi=10.1021/es0301166|last1=Moll|first1=H.|last2=Stumpf|first2=T.|last3=Merroun|first3=M.|last4=Rossberg|first4=A.|last5=Selenska-Pobell|first5=S.|last6=Bernhard|first6=G.|title=Time-resolved laser fluorescence spectroscopy study on the interaction of curium(III) with Desulfovibrio äspöensis DSM 10631T|journal=Environmental Science & Technology|volume=38|issue=5|pages=1455–1459|date=2004|pmid=15046347|bibcode = 2004EnST...38.1455M }}</ref><ref>{{cite journal|author=Ozaki, T.|display-authors=etal|url=http://sciencelinks.jp/j-east/article/200305/000020030503A0110480.php|archive-url=https://web.archive.org/web/20090225195752/http://sciencelinks.jp/j-east/article/200305/000020030503A0110480.php|url-status=dead|archive-date=2009-02-25|title=Association of Eu(III) and Cm(III) with Bacillus subtilis and Halobacterium salinarium|journal=Journal of Nuclear Science and Technology|date=2002|volume=Suppl. 3|pages=950–953|doi=10.1080/00223131.2002.10875626|bibcode=2002JNST...39S.950O |s2cid=98319565}}</ref> and in the laboratory both americium and curium were found to support the growth of [[methylotroph]]s.<ref>{{cite journal |last1=Remick |first1=Kaleigh |last2=Helmann |first2=John D. |title=The Elements of Life: A Biocentric Tour of the Periodic Table |journal=Advances in Microbial Physiology |publisher=PubMed Central |date=30 January 2023 |volume=82 |pages=1–127 |doi=10.1016/bs.ampbs.2022.11.001 |pmid=36948652 |pmc=10727122 |isbn=978-0-443-19334-7}}</ref>

==Applications==
===Radionuclides===
[[File:Curium self-glow radiation.jpg|thumb|right|[[Ionized air glow]] from curium alpha-radiation creates a purple aura in the dark.]]
Curium is one of the most radioactive isolable elements. Its two most common isotopes <sup>242</sup>Cm and <sup>244</sup>Cm are strong alpha emitters (energy 6&nbsp;MeV); they have fairly short half-lives, 162.8 days and 18.1 years, and give as much as 120&nbsp;W/g and 3&nbsp;W/g of heat, respectively.<ref name="CRC" /><ref name="Binder">Binder, Harry H.: ''Lexikon der chemischen Elemente'', S. Hirzel Verlag, Stuttgart 1999, {{ISBN|3-7776-0736-3}}, pp.&nbsp;174–178.</ref><ref>''Gmelin Handbook of Inorganic Chemistry'', System No. 71, Volume 7a, transuranics, Part A2, p. 289</ref> Therefore, curium can be used in its common oxide form in [[radioisotope thermoelectric generator]]s like those in spacecraft. This application has been studied for the <sup>244</sup>Cm isotope, while <sup>242</sup>Cm was abandoned due to its prohibitive price, around 2000&nbsp;USD/g. <sup>243</sup>Cm with a ~30-year half-life and good energy yield of ~1.6&nbsp;W/g could be a suitable fuel, but it gives significant amounts of harmful [[Gamma ray|gamma]] and [[Beta particle|beta]] rays from radioactive decay products. As an α-emitter, <sup>244</sup>Cm needs much less radiation shielding, but it has a high spontaneous fission rate, and thus a lot of neutron and gamma radiation. Compared to a competing thermoelectric generator isotope such as <sup>238</sup>Pu, <sup>244</sup>Cm emits 500 times more neutrons, and its higher gamma emission requires a shield that is 20 times thicker—{{convert|2|in|mm}} of lead for a 1&nbsp;kW source, compared to {{convert|0.1|in|mm}} for <sup>238</sup>Pu. Therefore, this use of curium is currently considered impractical.<ref name="lect">[http://fti.neep.wisc.edu/neep602/SPRING00/lecture5.pdf Basic elements of static RTGs] {{Webarchive|url=https://web.archive.org/web/20130215003518/http://fti.neep.wisc.edu/neep602/SPRING00/lecture5.pdf |date=2013-02-15 }}, G.L. Kulcinski, NEEP 602 Course Notes (Spring 2000), Nuclear Power in Space, University of Wisconsin Fusion Technology Institute (see last page)</ref>

A more promising use of <sup>242</sup>Cm is for making <sup>238</sup>Pu, a better radioisotope for thermoelectric generators such as in heart pacemakers. The alternate routes to <sup>238</sup>Pu use the (n,γ) reaction of <sup>237</sup>Np, or [[deuterium|deuteron]] bombardment of uranium, though both reactions always produce <sup>236</sup>Pu as an undesired by-product since the latter decays to <sup>232</sup>U with strong gamma emission.<ref>[http://www.kronenberg.kernchemie.de/ Kronenberg, Andreas], [http://www.kernenergie-wissen.de/pu-batterien.html Plutonium-Batterien] {{Webarchive|url=https://web.archive.org/web/20131226011403/http://www.kernenergie-wissen.de/pu-batterien.html |date=2013-12-26 }} (in German)

 {{Cite web |url=http://www.kronenberg.kernchemie.de/ |title=Archived copy |access-date=April 28, 2011 |archive-url=https://web.archive.org/web/20110221040021/http://www.kronenberg.kernchemie.de/ |archive-date=February 21, 2011 |url-status=bot: unknown |df=mdy-all }}</ref> Curium is a common starting material for making higher [[transuranium element|transuranic]] and [[superheavy element]]s. Thus, bombarding <sup>248</sup>Cm with neon (<sup>22</sup>Ne), magnesium (<sup>26</sup>Mg), or calcium ([[calcium-48|<sup>48</sup>Ca]]) yields isotopes of [[seaborgium]] (<sup>265</sup>Sg), [[hassium]] (<sup>269</sup>Hs and <sup>270</sup>Hs), and [[livermorium]] (<sup>292</sup>Lv, <sup>293</sup>Lv, and possibly <sup>294</sup>Lv).<ref name="HOWI_1980">Holleman, pp. 1980–1981.</ref> Californium was discovered when a microgram-sized target of curium-242 was irradiated with 35&nbsp;MeV [[alpha particle]]s using the {{convert|60|in|cm|adj=on}} cyclotron at Berkeley:
:{{nuclide|curium|242}} + {{nuclide|helium|4}} → {{nuclide|californium|245}} + {{nuclide|neutronium|1}}
Only about 5,000 atoms of californium were produced in this experiment.<ref>{{cite book|title=One Hundred Years after the Discovery of Radioactivity|editor=Adloff, J. P.|last=Seaborg|first=Glenn T.|page=82|date=1996|publisher=Oldenbourg Wissenschaftsverlag|isbn=978-3-486-64252-0}}</ref>

The odd-mass curium isotopes <sup>243</sup>Cm, <sup>245</sup>Cm, and <sup>247</sup>Cm are all highly [[fissile material|fissile]] and can release additional energy in a thermal spectrum [[nuclear reactor]]. All curium isotopes are fissionable in fast-neutron reactors. This is one of the motives for [[minor actinide]] separation and transmutation in the [[nuclear fuel cycle]], helping to reduce the long-term radiotoxicity of used, or [[spent nuclear fuel]].

[[File:MER APXS PIA05113.jpg|thumb|Alpha-particle X-ray spectrometer of a Mars exploration rover]]

===X-ray spectrometer===
The most practical application of <sup>244</sup>Cm—though rather limited in total volume—is as α-particle source in [[alpha particle X-ray spectrometer]]s (APXS). These instruments were installed on the [[Mars Pathfinder|Sojourner]], [[Mars rover|Mars]], [[Mars 96]], [[Mars Exploration Rover]]s and [[Philae (spacecraft)|Philae comet lander]],<ref>{{cite web|url=http://www.bernd-leitenberger.de/philae.shtml |title=Der Rosetta Lander Philae |publisher=Bernd-leitenberger.de |date=2003-07-01 |access-date=2011-03-25}}</ref> as well as the [[Mars Science Laboratory]] to analyze the composition and structure of the rocks on the surface of planet [[Mars]].<ref>{{cite journal|bibcode=1996DPS....28.0221R|title=An Alpha Proton X-Ray Spectrometer for Mars-96 and Mars Pathfinder|author=Rieder, R.|author2=Wanke, H.|author3=Economou, T.|journal=Bulletin of the American Astronomical Society|volume=28|page=1062|date=September 1996}}</ref> APXS was also used in the [[Surveyor program|Surveyor 5–7]] moon probes but with a <sup>242</sup>Cm source.<ref name="LA2">[http://www.ead.anl.gov/pub/doc/curium.pdf Human Health Fact Sheet on Curium] {{Webarchive|url=https://web.archive.org/web/20060218162709/http://www.ead.anl.gov/pub/doc/curium.pdf |date=2006-02-18 }}, Los Alamos National Laboratory</ref><ref>Leitenberger, Bernd [http://www.bernd-leitenberger.de/surveyor.shtml Die Surveyor Raumsonden] (in German)</ref><ref>{{cite book|chapter-url=https://history.nasa.gov/SP-480/ch9.htm |author=Nicks, Oran |
chapter=Ch. 9. Essentials for Surveyor|publisher=NASA|date=1985|title=SP-480 Far Travelers: The Exploring Machines}}</ref>

An elaborate APXS setup has a sensor head containing six curium sources with a total decay rate of several tens of [[Curie (unit)|millicuries]] (roughly one [[gigabecquerel]]). The sources are collimated on a sample, and the energy spectra of the alpha particles and protons scattered from the sample are analyzed (proton analysis is done only in some spectrometers). These spectra contain quantitative information on all major elements in the sample except for hydrogen, helium and lithium.<ref>[https://web.archive.org/web/20060302040531/http://athena.cornell.edu/pdf/tb_apxs.pdf Alpha Particle X-Ray Spectrometer (APXS)], Cornell University</ref>

==Safety==
Due to its radioactivity, curium and its compounds must be handled in appropriate labs under special arrangements. While curium itself mostly emits α-particles which are absorbed by thin layers of common materials, some of its decay products emit significant fractions of beta and gamma rays, which require a more elaborate protection.<ref name="lenntech" /> If consumed, curium is excreted within a few days and only 0.05% is absorbed in the blood. From there, ~45% goes to the [[liver]], 45% to the bones, and the remaining 10% is excreted. In bone, curium accumulates on the inside of the interfaces to the [[bone marrow]] and does not significantly redistribute with time; its radiation destroys bone marrow and thus stops [[red blood cell]] creation. The [[biological half-life]] of curium is about 20 years in the liver and 50 years in the bones.<ref name="lenntech" /><ref name="LA2" /> Curium is absorbed in the body much more strongly via inhalation, and the allowed total dose of <sup>244</sup>Cm in soluble form is 0.3&nbsp;μ[[Curie (unit)|Ci]].<ref name="CRC" /> Intravenous injection of <sup>242</sup>Cm- and <sup>244</sup>Cm-containing solutions to rats increased the incidence of [[bone tumor]], and inhalation promoted [[lung]] and [[liver cancer]].<ref name="lenntech" />

Curium isotopes are inevitably present in spent nuclear fuel (about 20 g/tonne).<ref>Hoffmann, K. ''Kann man Gold machen? Gauner, Gaukler und Gelehrte. Aus der Geschichte der chemischen Elemente'' (Can you make gold? Crooks, clowns and scholars. From the history of the chemical elements), Urania-Verlag, Leipzig, Jena, Berlin 1979, no ISBN, p. 233</ref> The isotopes <sup>245</sup>Cm–<sup>248</sup>Cm have decay times of thousands of years and must be removed to neutralize the fuel for disposal.<ref>Baetslé, L. H. [http://www.ictp.trieste.it/~pub_off/lectures/lns012/Baetsle.pdf Application of Partitioning/Transmutation of Radioactive Materials in Radioactive Waste Management] {{Webarchive|url=https://web.archive.org/web/20050426092418/http://www.ictp.trieste.it/~pub_off/lectures/lns012/Baetsle.pdf |date=2005-04-26 }}, Nuclear Research Centre of Belgium Sck/Cen, Mol, Belgium, September 2001.</ref> Such a procedure involves several steps, where curium is first separated and then converted by neutron bombardment in special reactors to short-lived nuclides. This procedure, [[nuclear transmutation]], while well documented for other elements, is still being developed for curium.<ref name="denecke" />

== References ==
{{Reflist|30em}}

==Bibliography==
* {{Greenwood&Earnshaw2nd}}
* Holleman, Arnold F. and Wiberg, Nils '' Lehrbuch der Anorganischen Chemie'', 102 Edition, de Gruyter, Berlin 2007, {{ISBN|978-3-11-017770-1}}.
* Penneman, R. A. and Keenan T. K. [http://www.osti.gov/bridge/purl.cover.jsp?purl=/4187189-IKQUwY/ The radiochemistry of americium and curium], University of California, Los Alamos, California, 1960

==External links==
{{Commons}}
{{wiktionary|curium}}
* [http://www.periodicvideos.com/videos/096.htm Curium] at ''[[The Periodic Table of Videos]]'' (University of Nottingham)
* [http://toxnet.nlm.nih.gov/cgi-bin/sis/search/r?dbs+hsdb:@term+@na+@rel+curium,+radioactive NLM Hazardous Substances Databank – Curium, Radioactive]
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