Periodic Table/Fermium/²⁵⁷Fm

← 256Fm258Fm →

²⁵⁷Fm

Fermium-257

Radioactive· Half-life: 100 d

Nuclear Propertiesbinding energy · spin-parity · abundance

Protons (Z)

100

Neutrons (N)

157

Mass Number (A)

257

Atomic Mass

257.095105AMU

Spin / Parity

9/2+

Binding E/A

7.223keV

Natural Abundance

Trace / None

Half-life

100 d

Decay Modesoverview · half-life · α · β⁻ · β⁺

α

99.8%

SF

0.2%

Decay Chain

²⁵⁷FmFermium100 d

α99.8%

²⁵³CfCalifornium17.8 d

β⁻99.7%

α²⁴⁹Cm0.31%

²⁵³EsEinsteinium20.5 d

α100.0%

²⁴⁹BkBerkelium327 d

β⁻100.0%

α²⁴⁵Am0.00%

²⁴⁹CfCalifornium351 y

α100.0%

²⁴⁵CmCurium8.25 ky

α100.0%

²⁴¹PuPlutonium14.3 y

β⁻100.0%

α²³⁷U0.00%

²⁴¹AmAmericium433 y

α100.0%

²³⁷NpNeptunium2.14 My

α100.0%

30Mg²⁰⁷Tl4.00%

²³³PaProtactinium27.0 d

β⁻100.0%

²³³UUranium159 ky

α100.0%

24Ne²⁰⁹Pb7.20%

28Mg²⁰⁵Hg1.30%

²²⁹ThThorium7.92 ky

α100.0%

²²⁵RaRadium14.8 d

β⁻100.0%

²²⁵AcActinium9.92 d

α100.0%

¹⁴C²¹¹Bi5.30%

²²¹FrFrancium4.80 min

α100.0%

¹⁴C²⁰⁷Tl8.80%

β⁻²²¹Ra0.00%

²¹⁷AtAstatine32.6 ms

α100.0%

β⁻²¹⁷Rn0.01%

²¹³BiBismuth45.6 min

β⁻97.9%

α²⁰⁹Tl2.09%

²¹³PoPolonium3.71 μs

α100.0%

²⁰⁹PbLead3.23 h

β⁻100.0%

²⁰⁹BiBismuth20100000000 Gy

α100.0%

²⁰⁵TlThalliumSTABLE

21-step decay chain → stable · Primary path shown · branching ratios indicated

Other Isotopes of Fermium

241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260

← Back to FermiumData: IAEA NDS · ENSDF