编辑“︁钚”︁（章节）

== 特性 ==
=== 物理性質 ===
鈽和多數金屬一樣具銀灰色外表，尤與[[鎳]]特別相似，但它在[[二氧化鈽|氧化]]後會迅速轉為暗灰色（有時呈黃色或橄欖綠），而將其氧化後，會產生一定的熱能。<ref name = "WISER">{{cite web
|url = http://webwiser.nlm.nih.gov/getSubstanceData.do;jsessionid=89B673C34252C77B4C276F2B2D0E4260?substanceID=419&displaySubstanceName=Plutonium,%20Radioactive&UNNAID=&STCCID=&selectedDataMenuItemID=44
|author = NIH contributors
|publisher = U.S. National Library of Medicine, National Institutes of Health
|location = Bethesda (MD)
|title = Plutonium, Radioactive
|work = Wireless Information System for Emergency Responders (WISER)
|accessdate = 2008-11-23
|archive-url = https://www.webcitation.org/618bQEh1E?url=http://webwiser.nlm.nih.gov/getSubstanceData.do;jsessionid=89B673C34252C77B4C276F2B2D0E4260?substanceID=419
|archive-date = 2011-08-22
|dead-url = yes
}} (public domain text)</ref><ref>{{cite journal
|title = Nitric acid processing
|url = http://arq.lanl.gov/source/orgs/nmt/nmtdo/AQarchive/3rdQuarter08/page3.shtml
|journal = Actinide Research Quarterly
|author = ARQ staff
|year = 2008
|issue = 3rd quarter
|publisher = Los Alamos National Laboratory
|location = Los Alamos (NM)
|quote = While plutonium dioxide is normally olive green, samples can be various colors. It is generally believed that the color is a function of chemical purity, stoichiometry, particle size, and method of preparation, although the color resulting from a given preparation method is not always reproducible.
|accessdate = 2010-02-09
|archive-url = https://web.archive.org/web/20100527200643/http://arq.lanl.gov/source/orgs/nmt/nmtdo/AQarchive/3rdQuarter08/page3.shtml
|archive-date = 2010-05-27
|dead-url = yes
}}</ref>。鈽在室溫下以[[鈽的同核異構體|α型]]存在，是鈽元素最普遍的結構型態（[[同素異形體]]），質地如[[鑄鐵]]般堅而易脆，但與其他金屬製成[[合金]]後又變得柔軟而富延展性。鈽和多數金屬不同，它不是[[熱導率|熱]]和[[電導率|電]]的良好導體。它的[[熔點]]很低（640&nbsp;°C），而[[沸點]]異常的高（3327&nbsp;°C）<ref name = "WISER"/>。

鈽最普遍釋放的[[游離輻射]]類型是[[α衰變|α粒子發射]]（即釋放出高能的[[氦]]原子核）<ref name = "NNDC">{{cite web
|url = http://www.nndc.bnl.gov/chart/
|author = NNDC contributors
|author2= Alejandro A. Sonzogni (Database Manager)
|title = Chart of Nuclides
|publisher = National Nuclear Data Center, [[Brookhaven National Laboratory]]
|accessdate = 2008-09-13
|year = 2008
|location = Upton (NY)
|archive-date = 2011-07-21
|archive-url = https://web.archive.org/web/20110721051025/http://www.nndc.bnl.gov/chart/
}}</ref>。最典型的一種核子武器核心即是以5公斤（約12.5 × 10<sup>24</sup>個）鈽原子構成。由於鈽的半衰期為24,100年，故其每秒約有11.5 × 10<sup>12</sup>個鈽原子產生衰變，發射出5.157 [[電子伏特|MeV]]的α粒子，相當於9.68瓦特能量。α粒子的減速會釋放出熱能，使觸摸時感覺溫暖<ref>{{cite book
|last = Rhodes |first = Richard
|year = 1986
|title = The Making of the Atomic Bomb
|url = https://archive.org/details/makingofatomicbo00rich |isbn = 0-671-65719-4
|pages = [https://archive.org/details/makingofatomicbo00rich/page/659 659]–660
|publisher = Simon & Schuster
|location = New York}} Leona Marshall: "When you hold a lump of it in your hand, it feels warm, like a live rabbit"</ref>。

[[電阻率]]是表物質所能抵抗[[電流]]流經強度的物理量。鈽於室溫時的電阻率比一般金屬高很多，而且鈽和多數金屬相反，其電阻率隨溫度降低而提高<ref name="Miner1968p544">{{harvnb|Miner|1968|p = 544}}</ref>。但近期研究指出，當溫度降至100[[熱力學溫標|K]]以下時，鈽的電阻率會急遽降低<ref name = "Miner1968p544"/>。電阻率由於輻射損傷，會在20K之後逐漸提高，速率因同位素結構而異<ref name = "Miner1968p544"/>。

鈽具有自發輻射性質，使得晶體結構產生[[金屬疲勞|疲勞]]，即原有秩序的原子排列因為輻射而隨時間產生紊亂<ref name = "HeckerPlutonium" />。然而，當溫度上升超過100K時，自發輻射也能導致[[退火]]，削弱疲勞現象<ref>{{cite journal
|title = Aging of Plutonium and Its Alloys
|page = 242
|journal = Los Alamos Science
|year = 2000
|issue = 26
|url = http://library.lanl.gov/cgi-bin/getfile?00818029.pdf
|format = PDF
|last = Hecker
|first = Siegfried S.
|author2= Martz, Joseph C.
|location = Los Alamos, New Mexico
|publisher = Los Alamos National Laboratory
|accessdate = 2009-02-15
|archive-date = 2021-04-28
|archive-url = https://web.archive.org/web/20210428114802/https://library.lanl.gov/cgi-bin/getfile?00818029.pdf
}}</ref>。

鈽和多數金屬不同：它的密度在熔化時變大（約2.5%），但液態金屬的密度又隨溫度呈線性下降<ref name="Miner1968p544" />。另外，接近熔點時，鈽的液態金屬具有很高的[[黏度|黏性]]和[[表面張力係數|表面張力]]（相較於其他金屬）<ref name = "HeckerPlutonium"/>。

=== 同素異形體 ===
{{Main|鈽的同素異形體}}
[[File:Pu-phases.png|thumb|鈽因周圍壓力變化而有六種同素異形體：α、β、γ、δ、δ'及ε<ref name = "Baker1983"/>]]
在一般情況下，鈽有六種[[同素異形體]]，並在高溫、限定壓力範圍下有第七種（ζ）存在<ref name = "Baker1983">{{cite journal
|url = http://library.lanl.gov/cgi-bin/getfile?07-16.pdf
|title = Plutonium: A Wartime Nightmare but a Metallurgist's Dream
|last = Baker
|first = Richard D.
|author2= Hecker, Siegfried S.
|author3= Harbur, Delbert R.
|journal = Los Alamos Science
|year = 1983
|publisher = Los Alamos National Laboratory
|pages = 148, 150–151
|accessdate = 2009-02-15
|archive-date = 2011-10-17
|archive-url = https://web.archive.org/web/20111017034523/http://library.lanl.gov/cgi-bin/getfile?07-16.pdf
}}</ref><!-- Note: page 148 -->。這些同素異形體的[[內能]]相近，但擁有截然不同的[[密度]]和[[晶體結構]]。因此鈽對溫度、壓力以及化學性質的變化十分敏感，各同素異形體的體積並隨[[相變]]而具有極大差異性<ref name = "HeckerPlutonium">{{cite journal
|first = Siegfried S.
|last = Hecker
|title = Plutonium and its alloys: from atoms to microstructure
|journal = Los Alamos Science
|volume = 26
|year = 2000
|pages = 290–335
|url = http://www.fas.org/sgp/othergov/doe/lanl/pubs/00818035.pdf
|format = PDF
|accessdate = 2009-02-15
|archive-date = 2021-03-19
|archive-url = https://web.archive.org/web/20210319010158/https://fas.org/sgp/othergov/doe/lanl/pubs/00818035.pdf
}}</ref>。密度因同素異形體而異，範圍自16.00 g/cm<sup>3</sup>到19.86 g/cm<sup>3</sup>不等<ref name = "CRC2006p4-27">{{harvnb|CRC|2006|p = 4–27}}</ref>。

諸多同素異形體的存在，造成鈽的狀態易變，使鈽元素的製造變得非常困難。例如，α型存在於室溫的純鈽中。它和[[鑄鐵]]有許多相似加工後性質，但只要稍微提高溫度，便會轉成具有可塑性和可鍛造性的β型<ref name = "Miner1968p542">{{harvnb|Miner|1968|p = 542}}</ref>。造成鈽複雜相圖的背後因素迄今仍未被完整解惑。α型屬於低對稱性的[[單斜晶系|單斜]]結構，因此促成它的易碎性、強度、壓縮性及低傳導性<ref name = "Baker1983"/>。

=== 化合物與化學性質 ===
{{See also|:Category:鈽化合物|l1 = 鈽化合物}}
[[File:Plutonium in solution.jpg|thumb|right|300px|鈽在溶液中的各種氧化態|alt=五支盛裝著溶液試管：藍紫色、貼有標籤「Pu(III)」；深棕色、貼有標籤「Pu(IV)HClO4」；淺紫色、貼有標籤「Pu(V)」；淺棕色、貼有標籤「Pu(VI)」；墨綠色、貼有標籤「Pu(VII)」。]]
室溫時，純鈽金屬是銀灰色、但因氧化而鏽蝕{{sfn|Heiserman|1992|p=339}}。鈽在[[水溶液]]中形成四種離子[[氧化態]]<ref name = "CRC2006p4-27"/>：
*Pu(III) — Pu<sup>3+</sup>（藍紫色）
*Pu(IV) — Pu<sup>4+</sup>（黃棕色）
*Pu(V) — PuO<sub>2</sub><sup>+</sup>（粉紅色？）<ref group="註">PuO<sub>2</sub><sup>+</sup>離子在溶液中十分不穩定，所佔比例不比Pu<sup>4+</sup>和PuO<sub>2</sub><sup>2+</sup>；Pu<sup>4+</sup>又會將剩餘PuO<sub>2</sub><sup>+</sup>氧化成PuO<sub>2</sub><sup>2+</sup>，自身还原为Pu<sup>3+</sup>。因此，鈽水溶液會漸漸趨向Pu<sup>3+</sup> 和PuO<sub>2</sub><sup>2+</sup>的混合溶液。
:{{cite web
 |title       = Nuclear Criticality Safety Engineering Training Module 10 – Criticality Safety in Material Processing Operations, Part 1
 |url         = http://ncsp.llnl.gov/ncset/Module10.pdf
 |format      = PDF
 |accessdate  = 2006-02-15
 |year        = 2002
 |last        = Crooks
 |first       = William J.
 |deadurl     = yes
 |archiveurl  = https://web.archive.org/web/20060320153404/http://ncsp.llnl.gov/ncset/Module10.pdf
 |archivedate = 2006-03-20
}}</ref>
*Pu(VI) — PuO<sub>2</sub><sup>2+</sup>（粉桔色）
*Pu(VII) — PuO<sub>5</sub><sup>3−</sup>（綠色）–七價離子較稀有

鈽溶液所呈現的顏色決定於氧化態和酸[[離子|陰離子]]的性質<ref>{{cite book|last=Matlack|first=George|title=A Plutonium Primer: An Introduction to Plutonium Chemistry and its Radioactivity|publisher=Los Alamos National Laboratory|year=2002|id=LA-UR-02-6594|url=https://doctorspot.in/articles/a-plutonium-primer-an-introduction-to-plutonium-chemistry-and-its-radioactivity/|access-date=2024-09-04|archive-date=2024-09-04|archive-url=https://web.archive.org/web/20240904085238/https://doctorspot.in/articles/a-plutonium-primer-an-introduction-to-plutonium-chemistry-and-its-radioactivity/|dead-url=no}}</ref>。鈽的酸陰離子種類影響了[[配合物|錯合]]（原子與中心原子結合）的程度。

=== 核分裂 ===
[[File:Plutonium ring.jpg|150px|thumb|電解法精煉的[[武器級]]鈽元素環狀物。環狀物重5.3公斤，直徑約11公分，足夠製作一枚[[氫彈|核彈]]。它的形狀有助於維繫[[核臨界安全|臨界安全]]。|alt=生鏽的圓柱狀金屬]]

鈽是一種具放射性的[[錒系元素]]。它的[[電子排布|5f電子]]是離域和定域之間的過渡界線；鈽因此常被認為是最複雜的元素之一<ref name="physicsworld.com">{{cite news|url=http://physicsworld.com/cws/article/news/16443|title=Plutonium is also a superconductor|publisher=PhysicsWeb.org|author=Dumé, Belle|date=2002-11-20|accessdate=2010-09-18|archive-date=2012-01-12|archive-url=https://web.archive.org/web/20120112184014/http://physicsworld.com/cws/article/news/16443}}</ref>。它的[[同位素]][[鈽-239]]是三個最重要的[[核裂變|易裂變]]同位素之一（另外二者為[[鈾-233]]和[[鈾-235]]）<ref>{{cite web|url = http://www.epa.gov/rpdweb00/glossary/termdef.html#f|title = Fissile Material|work = Radiation Glossary|publisher = United States Environmental Protection Agency|year = 2008|accessdate = 2008-11-23|author = EPA contributors|archive-date = 2011-07-20|archive-url = https://web.archive.org/web/20110720044749/http://www.epa.gov/rpdweb00/glossary/termdef.html#f}}</ref>；[[鈽-241]]也具有高度易裂變性。所謂的具「易裂變性」（fissile），是指同位素的[[原子核]]受到[[中子溫度|慢中子]]撞擊後，能夠產生[[核分裂]]，並另釋放出足以支持[[核連鎖反應]]、進一步促使原子核分裂的中子。

=== 同位素 ===
{{Main|鈽的同位素}}
鈽有二十種已知的[[同位素]]，全部都具有[[放射性]]。其中壽命最長的是鈽-244（半衰期為8080萬年），也是所有[[超鈾元素]]中半衰期最長的[[核種]]。其他較長壽的同位素有鈽-242（半衰期為373300年）及鈽-239（半衰期為24110年）。其餘的[[放射性同位素]]半衰期都低於7000年。鈽也有八種[[同核異構體]]，但並不穩定、半衰期都不超過一秒<ref name = "NNDC"/>。钚-244存在于太空中。<ref name="WallnerFaestermann2015">{{cite journal|last1=Wallner|first1=A.|last2=Faestermann|first2=T.|last3=Feige|first3=J.|last4=Feldstein|first4=C.|last5=Knie|first5=K.|last6=Korschinek|first6=G.|last7=Kutschera|first7=W.|last8=Ofan|first8=A.|last9=Paul|first9=M.|last10=Quinto|first10=F.|last11=Rugel|first11=G.|last12=Steier|first12=P.|title=Abundance of live 244Pu in deep-sea reservoirs on Earth points to rarity of actinide nucleosynthesis|journal=Nature Communications|volume=6|year=2015|pages=5956|issn=2041-1723|doi=10.1038/ncomms6956|pmid=25601158|pmc=4309418|arxiv=1509.08054|bibcode=2015NatCo...6.5956W}}</ref>

已知的鈽同位素的[[質量數]]範圍從228到247不等。其中質量數低於鈽-244（最穩定的鈽同位素）的同位素，主要的[[放射性|衰變方式]]是[[自發裂變]]和[[α衰變]]，衰變產物通常生成鈾（92個[[質子]]）和[[錼]]（93個質子）的同位素（忽略裂變過程產生之二子核的大範圍）。質量數大於鈽-244的同位素則以[[β衰變]]為主要衰變方式，衰變產物多為[[鋂]]（95個質子）。鈽-241是[[錼衰變系]]的母同位素，透過β衰變变成鋂-241。<ref name = "NNDC"/>{{sfn|Heiserman|1992|p=340}}。

鈽-238和鈽-239是最常用的人造同位素{{sfn|Heiserman|1992|p=338}}。鈽-239是用中子轰击鈾，透過下列反應合成的<ref>{{cite journal|first=J. W.|last=Kennedy|author2=Seaborg, G. T.|author3=Segrè, E.|author4=Wahl, A. C.|title=Properties of Element 94|journal=Physical Review|year=1946|issue=7–8|pages=555–556|doi=10.1103/PhysRev.70.555|volume=70}}</ref>：
:<math>\mathrm{^{238}_{\ 92}U\ +\ ^{1}_{0}n\ \longrightarrow \ ^{239}_{\ 92}U\ \xrightarrow[23.5 \ min]{\beta^-} \ ^{239}_{\ 93}Np\ \xrightarrow[2.3565 \ d]{\beta^-} \ ^{239}_{\ 94}Pu}</math>

鈾-235裂變中的中子被鈾-238原子核[[中子俘獲|俘獲]]、形成鈾-239；[[β衰變]]將一個中子轉變成質子，形成鎿-239（半衰期為2.36日），另一次β衰變則形成鈽-239<ref name = "Greenwood1997p1259">{{harvnb|Greenwood|1997|p = 1259}}</ref>。[[合金管工程]]的學者曾在1940年推導出此反應式。

鈽-238是以[[氘|氘核]]（D，重[[氫]]的原子核）撞擊鈾-238，透過下列反應合成<ref>{{cite journal|first=Glenn T.|last=Seaborg|author2=McMillan, E.|author3=Kennedy, J. W.|author4=Wahl, A. C.|title=Radioactive Element 94 from Deuterons on Uranium|journal=Physical Review|year=1946|issue=7–8|pages=366–367|doi=10.1103/PhysRev.69.367|volume=69}}</ref>：

:<math>\mathrm{^{238}_{\ 92}U\ +\ ^{2}_{1}D\ \longrightarrow \ ^{238}_{\ 93}Np\ +\ 2\ ^{1}_{0}n \quad;\quad ^{238}_{\ 93}Np\ \xrightarrow[2.117 \ d]{\beta^-} \ ^{238}_{\ 94}Pu}</math>

在此反應過程中，一個氘核撞擊[[鈾]]-238，生成兩個中子和鎿-238；[[鎿]]-238再發射β<sup>-</sup>粒子，形成鈽-238。{{sfn|Bernstein|2007|pp=76–77}}钚-238也可以由[[镎-237]][[中子活化]]而成。<ref>{{cite web |url=https://www.energy.gov/sites/prod/files/NEGTN0NEAC_PU-238_042108.pdf |title=Assessment of Plutonium-238 Production of Alternatives: Briefing for Nuclear Energy Advisory Committee |publisher=Energy.gov |last=Miotla |first=Dennis |date=21 April 2008 |access-date=28 February 2022 |archive-date=March 16, 2022 |archive-url=https://web.archive.org/web/20220316130014/https://www.energy.gov/sites/prod/files/NEGTN0NEAC_PU-238_042108.pdf |url-status=live }}</ref>

=== 衰變熱與裂變性質 ===
鈽同位素會發生放射性衰變，釋放出[[衰變熱]]。不同的同位素，單位質量所釋出的熱量也有所差異。衰變熱的單位通常以「瓦特/公斤」或「毫瓦特/公克」計。<!--In case of...may be significant.-->所有同位素在衰變時都會釋放出微弱的伽馬射線。
{| class="wikitable" align="center"
|+ 鈽同位素的衰變熱<ref>{{cite web|url=http://www.cnfc.or.jp/e/proposal/reports/index.html|title=Can Reactor Grade Plutonium Produce Nuclear Fission Weapons?|date=May 2001|publisher=Council for Nuclear Fuel Cycle Institute for Energy Economics, Japan|access-date=2010-09-19|archive-date=2021-02-24|archive-url=https://web.archive.org/web/20210224141047/http://www.cnfc.or.jp/e/proposal/reports/index.html}}</ref>
!width="10%"| 同位素 !!width="20%"| [[放射性#種類|衰變方式]] !! [[半衰期]]（年） !! [[衰變熱]]（W/kg） !! [[自發裂變]]中子（1/(g·s)） !! 簡介
|-
! [[鈽-238]]
| [[α衰變]]成為[[鈾-234]]
| 87.74
| 560
| 2600
| 衰變熱極高。即使量少也能顯著自燃。使用於[[放射性同位素熱電機]]。
|-
! [[鈽-239]]
| α衰變成為[[鈾-235]]
| 24100
| 1.9
| 0.022
| 現最主要使用的易裂變同位素。
|-
! [[鈽-240]]
| α衰變成為[[鈾-236]]<br />自發裂變
| 6560
| 6.8
| 910
| 鈽-239同位素的主要雜質。<!--The plutonium grade...use in nuclear weapons.-->
|-
! [[鈽-241]]
| [[β衰變]]成為[[鋂-241]]
| 14.4
| 4.2
| 0.049
| 衰變成為鋂-241；輻射危害的早期研究對象。
|-
! [[鈽-242]]
| α衰變成為[[鈾-238]]
| 376000
| 0.1
| 1700
| 
|}