錼只痕量存在於自然界，通常由人工合成製得，因此無法確定。錼有從 219Np 至 244Np（不包括 221Np）共 25 種同位素，沒有一個是穩定的。最長壽的放射性同位素是 237Np，半衰期 2144 萬年。 圖表 styletextalignright 93 styletextalignright 132 22503391 8 3 ms 2 µs 221Pa 92 styletextalignright 93 styletextalignright 133 22603515 10 35 10 ms 222Pa rowspan2 rowspan2 styletextalignright 93 rowspan2 styletextalignright 134 rowspan222703496 8 rowspan2510 60 ms 9995 223Pa rowspan252 rowspan2 05 227U rowspan3 rowspan3 styletextalignright 93 rowspan3 styletextalignright 135 rowspan322803618 21 rowspan3614 14 s 59 228U rowspan3 rowspan3 41 224Pa SF 012 various rowspan2 rowspan2 styletextalignright 93 rowspan2 styletextalignright 136 rowspan222903626 9 rowspan240 2 min 51 225Pa rowspan252 rowspan2 49 229U rowspan2 rowspan2 styletextalignright 93 rowspan2 styletextalignright 137 rowspan223003783 6 rowspan246 3 min 97 230U rowspan2 rowspan2 3 226Pa rowspan2 rowspan2 styletextalignright 93 rowspan2 styletextalignright 138 rowspan223103825 5 rowspan2488 2 min 98 231U rowspan252 rowspan2 2 227Pa rowspan2 rowspan2 styletextalignright 93 rowspan2 styletextalignright 139 rowspan223204011 11 rowspan2147 3 min 9999 232U rowspan24 rowspan2 003 228Pa rowspan2 rowspan2 styletextalignright 93 rowspan2 styletextalignright 140 rowspan223304074 5 rowspan2362 1 min 9999 233U rowspan252 rowspan2 001 229Pa styletextalignright 93 styletextalignright 141 234042895 9 44 1 d 234U 0 rowspan2 rowspan2 styletextalignright 93 rowspan2 styletextalignright 142 rowspan22350440633 21 rowspan23961 12 d 235U rowspan252 rowspan2 0026 231Pa rowspan3Fissile nuclide rowspan3 styletextalignright 93 rowspan3 styletextalignright 143 rowspan323604657 5 rowspan3154 6105 y 873 236U rowspan36 rowspan3 125 236Pu 16 232Pa rowspan2 styletextindent1em rowspan2 colspan3 styletextindent2em 60 50 keV rowspan2225 4 h 52 236U rowspan21 rowspan2 48 236Pu rowspan3 最常見同位素 rowspan3 styletextalignright 93 rowspan3 styletextalignright 144 rowspan32370481734 20 rowspan32144 7106 y 233Pa rowspan352 rowspan3 痕量由鈾的中子捕獲產生 21010 various 41012 207Tl30Mg styletextalignright 93 styletextalignright 145 2380509464 20 2117 2 d 238Pu 2 styletextindent1em colspan3 styletextindent2em 2300 200 keV 112 39 ns styletextalignright 93 styletextalignright 146 2390529390 22 2356 3 d 239Pu 52 痕量 styletextalignright 93 styletextalignright 147 240056162 16 619 2 min 240Pu 5 痕量 244Pu 的衰變產物 rowspan2 styletextindent1em rowspan2 colspan3 styletextindent2em 20 15 keV rowspan2722 2 min 9989 240Pu rowspan21 rowspan2 IT 11 240Np styletextalignright 93 styletextalignright 148 24105825 8 139 2 min 241Pu 52 styletextalignright 93 styletextalignright 149 24206164 21 22 2 min 242Pu 1 styletextindent1em colspan3 styletextindent2em 0 50 keV 55 1 min 6 styletextalignright 93 styletextalignright 150 24306428 3 185 15 min 243Pu 52 styletextalignright 93 styletextalignright 151 24406785 32 229 16 min 244Pu 7 參考文獻 Isotope masses from Ame2003 Atomic Mass Evaluation by G Audi AH Wapstra C Thibault J Blachot and O Bersillon in Nuclear Physics A729 2003 Halflife spin and isomer data selected from these sources Editing notes on this articles talk page Audi Bersillon Blachot Wapstra The Nubase2003 evaluation of nuclear and decay properties Nuc Phys A 729 pp 3128 2003 National Nuclear Data Center Brookhaven National Laboratory Information extracted from the NuDat 21 database retrieved Sept 2005 David R Lide ed Norman E Holden in CRC Handbook of Chemistry and Physics 85th Edition online version CRC Press Boca Raton Florida 2005 Section 11 Table of the Isotopes Np Category 錼的同位素