neptunium chemical element britannica neptunium np radioactive chemical element actinoid series periodic table transuranium element artificially produce atomic number trace neptunium subsequently find nature primeval produce neptunium encyclopedia encyclopeadia britannica article neptunium learn related britannica article browse search quiz game day login subscribe entertainment pop culture geography travel health medicine lifestyles social issues literature philosophy religion politics law government science sports recreation technology visual art world history quiz games podcast day biographies week review topic summaries infographics demystified lists wtfact companions image galleries spotlight entertainment pop culture geography travel health medicine lifestyles social issues literature philosophy religion politics law government science sports recreation technology visual art world history britannica classics check retro video encyclopedia britannica archive wtfact video wtfact britannica share bizarre fact find demystified videos demystified britannica answer burn question time history video find happen month month history britannica explain video britannica explain variety topic answer frequently ask question neptunium article media additional info home science chemistry chemical element print cite share share share social medium facebook twitter url feedback external website feedback correction update omission let know suggestion improve article require login feedback type select type required factual correction spelling grammar correction link correction additional information feedback submit feedback thank feedback editor review submit determine revise article join britannica publishing partner program community expert gain global audience work external websites royal society chemistry neptunium chemicool neptunium element facts los alamos national laboratory chemistry division neptunium livescience facts neptunium chemical neptunium britannica websites articles britannica encyclopedias elementary high school student neptunium student encyclopedia age written lester morss adjunct professor department chemistry university maryland college park maryland article history alternative title np neptunium np radioactive chemical element actinoid series periodic table transuranium element artificially produce atomic number trace neptunium subsequently find nature primeval produce neutron transmutation reaction uranium ore american physicist edwin mcmillan chemist philip abelson find neptunium uranium bombard neutron cyclotron berkeley california element name planet neptune planet uranus encyclopædia britannica britannica quiz names symbols periodic table quiz periodic table element know symbol quiz show chemical symbol need choose chemical element represent neptunium produce weighable amount nuclear reactor breeder reactor product plutonium production neptunium produce part plutonium neptunium isotope radioactive stable half life year unstable half life microsecond separate reactor fuel study physical chemical property element neptunium silvery metal exist crystalline modification room temperature form alpha orthorhombic neptunium chemically reactive similar plutonium uranium oxidation state neptunium ion aqueous solution possess characteristic colour np pale purple np pale yellow green npo green blue npo vary colourless pink yellow green depend anion present np dark green compound neptunium prepare oxidation state generally similar compound uranium plutonium oxidation state element properties atomic number stable isotope melt point c f specific gravity alpha oxidation state electron configuration gaseous atomic state f d s lester morss related britannica article actinoid element general similarity actinoid element discover neptunium atomic number prepare bombardment uranium metal neutron nuclear weapon produce control chain reaction discover element name neptunium planet uranus uranium name infer element decay element bohr wheeler fission theory suggest isotope new element fission low speed neutron bombardment transuranium element discovery transuranium element name neptunium history fingertip sign happen day day inbox email address sign agree privacy notice thank subscribe lookout britannica newsletter trust story deliver right inbox neptunium quick facts key people edwin mattison mcmillan philip hauge abelson relate topic chemical element neptunium series inspire inbox sign daily fun fact day history update special offer enter email subscribe sign email agree news offer information encyclopaedia britannica click view privacy notice easy unsubscribe link provide email thank subscribe lookout britannica newsletter trust story deliver right inbox stay connected facebook twitter youtube instagram pinterest newsletter legal info partner program contact privacy notice term use encyclopædia britannica close late episode parent feature topic empathy