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Neptunium

chemical element
Written By:

  • Lester Morss
See Article History

Alternative Title:
Np

Neptunium (Np), radioactive chemical element of the actinoid series of the periodic table that was the first transuranium element to be artificially produced, atomic number 93. Though traces of neptunium have subsequently been found in nature, where it is not primeval but produced by neutron -induced transmutation reactions in uranium ores, American physicist Edwin M. McMillan and chemist Philip H. Abelson first found neptunium in 1940 after uranium had been bombarded by neutrons from the cyclotron at Berkeley, California. The element was named after the planet Neptune , which is the first planet beyond Uranus .

Read More on This Topic

periodic table

actinoid element: General similarities of the actinoid elements

…to be discovered (1940) was neptunium, atomic number 93, which was prepared by bombardment of uranium metal with neutrons.

Neptunium has been produced in weighable amounts in nuclear reactors . In breeder reactors it is a by-product of plutonium production from uranium-238 (about one part neptunium is produced for every 1,000 parts plutonium). All neptunium isotopes are radioactive; the stablest is neptunium-237 , with a half-life of 2,144,000 years, and among the most unstable is neptunium-225, with a half-life of more than 2 microseconds. Neptunium-237 can be separated from used reactor fuel to study the physical and chemical properties of the element.

Neptunium, a silvery metal , exists in three crystalline modifications; the room-temperature form (alpha) is orthorhombic. Neptunium is chemically reactive and is more similar to plutonium than to uranium, with oxidation states from +3 to +7. Neptunium ions in aqueous solution possess characteristic colours: Np3+, pale purple; Np4+, pale yellow-green; NpO2+, green-blue; NpO22+, varying from colourless to pink or yellow-green, depending on the anion present; and Np7+, dark green. Compounds of neptunium have been prepared in all oxidation states +3 to +7; they are generally similar to compounds of uranium and plutonium with the same oxidation state .

Element Properties
atomic number93
stablest isotope237
melting point640 °C (1,184 °F)
specific gravity (alpha)20.45
oxidation states+3, +4, +5, +6, +7
electron configuration of gaseous atomic state[Rn]5f 46d17s2

Lester Morss

Learn More in these related Britannica articles:

  • periodic table

    actinoid element: General similarities of the actinoid elements
    …to be discovered (1940) was neptunium, atomic number 93, which was prepared by bombardment of uranium metal with neutrons.…
  • A test of a U.S. thermonuclear weapon (hydrogen bomb) at Enewetak atoll in the Marshall Islands, Nov. 1, 1952.

    nuclear weapon: Producing a controlled chain reaction
    …discovered element 93 (naming it neptunium, after the next planet after Uranus, for which uranium was named); they inferred that this element would decay into element 94. The Bohr and Wheeler fission theory suggested that one of the isotopes of this new element might also fission under low-speed neutron bombardment.…
  • periodic table

    transuranium element: Discovery of the first transuranium elements
    It was named neptunium.…
  • uranium processing: Conversion to plutonium
    …effectively transformed into the element neptunium (Np; with an atomic number of 93, one more than uranium). Neptunium-239 in turn undergoes beta decay, being transformed into plutonium-239 (atomic number 94).…
  • Edwin Mattison McMillan.

    Edwin Mattison McMillan
    …studying nuclear fission, McMillan discovered neptunium, a decay product of uranium-239. In 1940, in collaboration with Philip H. Abelson, he isolated the new element and obtained final proof of his discovery. Neptunium was the first of a host of transuranium elements that provide important nuclear fuels and contributed greatly to…

More About Neptunium

6 references found in Britannica articles

Assorted References

    • major reference
      • In actinoid element: General similarities of the actinoid elements
    • conversion from uranium-239
      • In uranium processing: Conversion to plutonium

    discovery

    • In nuclear weapon: Producing a controlled chain reaction
    • Abelson
      • In Philip Hauge Abelson
    • McMillan
      • In Edwin Mattison McMillan

    structure and properties

      • transuranium elements
        • In transuranium element: Discovery of the first transuranium elements

      External Websites

      • Royal Society of Chemistry – Neptunium
      • Chemicool – Neptunium Element Facts
      • Los Alamos National Laboratory’s Chemistry Division – Neptunium
      • LiveScience – Facts about Neptunium
      • Chemical Elements.com – Neptunium
      Britannica Websites
      Articles from Britannica Encyclopedias for elementary and high school students.
      • Neptunium – Student Encyclopedia (Ages 11 and up)

      Article History

      Article Contributors


      Feedback

      Corrections? Updates? Help us improve this article!
      Contact our editors with your feedback.



      Neptunium
      Chemical element

      chemical properties of Neptunium (part of Periodic Table of the Elements imagemap)

      key people
      • Edwin Mattison McMillan
      • Philip Hauge Abelson
      related topics
      • Chemical element
      • Neptunium series
      • Neptunium-239
      • Neptunium-237



      Similar Topics
      • Hydrogen
      • Carbon
      • Sodium
      • Nitrogen
      • Sulfur
      • Phosphorus
      • Boron
      • Iodine
      • Fluorine
      • Zinc

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      Neptunium
      Chemical element



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      Neptunium (Np)

      • Neptunium
      • Isotopes
      • Photos/Videos
      • ← Uranium
      • Plutonium →

      General Properties

      SymbolNp
      Atomic Number93
      Atomic Weight(237)
      Group
      (Actinoids)
      Solid, Conductor, Actinide, Radioactive, Synthetic
      Period7
      Blockf

      Physical Properties

      Density 20.2 g/cm3
      Atomic Volume 21.1 cm3/mole
      Atomic Radius 1.3 angstroms
      Covalent Radius
      Crust Abundance None
      Crystal StructureOrthorhombic
      Color Silver

      States

      Melting Point 640.0 °C
      Boiling Point 3900.0 °C
      Heat of Fusion
      Heat of Vaporization

      Energy

      Electronegativity 1.4 (Pauling Scale)
      Electron Affinity
      1st Ionization Energy 605 kJ/mol
      Specific Heat Capacity J g−1 K−1
      Thermal Conductivity 6.3 W·m−1·K−1

      Electrons & Oxidation

      Oxidation States+5,3,4,6
      Electrons Per Shell2 8 18 32 22 9 2
      Electron Configuration[Rn] 5f4 6d1 7s2
      1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6 4f14 5d10 6s2 6p6 5f4 6d1 7s2
      Orbital Diagram
      1s
      ↿⇂
      2s
      ↿⇂
      2p
      ↿⇂
      ↿⇂
      ↿⇂
      3s
      ↿⇂
      3p
      ↿⇂
      ↿⇂
      ↿⇂
      3d
      ↿⇂
      ↿⇂
      ↿⇂
      ↿⇂
      ↿⇂
      4s
      ↿⇂
      4p
      ↿⇂
      ↿⇂
      ↿⇂
      4d
      ↿⇂
      ↿⇂
      ↿⇂
      ↿⇂
      ↿⇂
      4f
      ↿⇂
      ↿⇂
      ↿⇂
      ↿⇂
      ↿⇂
      ↿⇂
      ↿⇂
      5s
      ↿⇂
      5p
      ↿⇂
      ↿⇂
      ↿⇂
      5d
      ↿⇂
      ↿⇂
      ↿⇂
      ↿⇂
      ↿⇂
      5f
      ↿ 
      ↿ 
      ↿ 
      ↿ 
       
       
       
      6s
      ↿⇂
      6p
      ↿⇂
      ↿⇂
      ↿⇂
      6d
      ↿ 
       
       
       
       
      6f
       
       
       
       
       
       
       
      7s
      ↿⇂
      7p
       
       
       
      7d
       
       
       
       
       
      7f
       
       
       
       
       
       
       

      Nuclear

      RadioactiveYes
      Half Life2.1455×106
      Lifetime3.0952×106y
      DecayAlpha Emission

      Media

      Planetary Bohr Model of Neptunium (Np)

      Lewis Dot Diagram of Neptunium (Np)

      Description
      Rare, silvery radioactive metal.
      Uses
      It has no significant commercial applications.
      Sources
      Produced by bombarding uranium with slow neutrons.
      Pronounciation (English)
      nep-TOO-ni-em

      Translations

      Afrikaans

      Neptunium
      Aragonese

      Neptunio
      العربية

      نبتونيوم
      Armãneashte

      Neptuniumu
      asturianu

      Neptuniu
      azərbaycan dili

      Neptunium
      български

      Нептуний
      বাংলা

      নেপচুনিয়াম
      brezhoneg

      Neptuniom
      bosanski

      Neptunij[um]
      Byelorussian

      Нептуній
      Cebuano

      Neptunyo
      čeština

      Neptunium
      Chuvash

      Нептуни
      Cymraeg

      Neptuni
      dansk

      Neptunium
      Deutsch

      Neptunium
      Ελληνικά

      Ποσeιδωνιο
      English

      Neptunium
      esperanto

      Neptunio
      español

      Neptunio
      eesti

      Neptuunium
      euskara

      Neptunioa
      فارسی

      نپتونیم
      suomi

      Neptunium
      føroyskt

      Neptunium
      français

      Neptunium
      furlan

      Netuni
      West-Frysk

      Neptunium
      Gaeilge

      Neiptiúiniam
      Gàidhlig

      Neiptiùiniam
      galego

      Neptunio
      ગુજરાતી

      નેપ્ટુનિયમનો
      Gaelg

      Nepçhunium
      Hakka Chinese

      Nai (錼)
      עברית

      נפטוניום
      हिन्दी

      नेप्ट्यूनियम
      hrvatski

      Neptunij
      magyar

      Neptúnium
      հայերեն

      Նեպտունիում
      Indonesia

      Neptunium
      íslenska

      Neptún
      italiano

      Nettunio
      日本語

      ネプツニウム
      ქართული

      ნეპტუნიუმი
      کٲشُر

      Neptun
      қазақ тілі

      Нептуний
      한국어

      넵투늄
      Kurdish

      Neptünyûm
      Komi

      Нептуний
      kernewek

      Neptunyum
      кыргызча

      Нептуний
      Latin

      Neptunium
      Lëtzebuergesch

      Neptunium
      Lombard

      Netüni
      lingála

      Netunu
      lietuvių

      Neptūnas
      latviešu

      Neptūnijs
      Mari

      Нептуний
      Maori

      Neptunium
      македонски

      Нептуниум
      മലയാളം

      നെപ്റ്റ്യൂണിയം
      монгол

      Нептуни
      Мокшан

      Нептуни
      Bahasa Melayu

      Neptunium
      Malti

      Neptunjum, ²Nettunju
      Nahuatl

      Tlāloctepoztli
      Nederlands

      Neptunium
      norsk

      Neptunium
      Occitan

      Neptuni
      ирон

      Нептуний
      polski

      Neptun
      português

      Neptúnio
      Runasimi

      Neptunyu
      română

      Neptuniu
      русский

      Нептуний
      slovenčina

      Neptunium
      slovenščina

      Neptunij
      Samoan

      Neptunimi
      Samogitian

      Neptūnas
      shqip

      Neptun, ²Neptuniumi
      српски

      Нептунијум
      Southern Sotho

      Neptuniamo
      svenska

      Neptunium
      Kiswahili

      Neptuni
      தமிழ்

      நெப்டூனியம்
      Tajik

      Нептуний
      ไทย

      เนปทูเนียม
      Türkçe

      Neptunyum
      ئۇيغۇرچە

      نېپتونىي
      українська

      Нептуній
      o‘zbek

      Neptuniy
      Tiếng Việt

      Neptuni
      Võro

      Neptuunium
      中文

      History

      Discovered In
      1940
      Discovered By
      Edwin M. McMillan and P. H. Abelson
      Discovered At
      USA
      Word Origin
      Named after "the planet Neptune"

      Links

      • Wikipedia: Neptunium
      • Web Elements: Neptunium
      • ChemiCool: Neptunium