Fermium-253 (Fm-253)

Identity

Protons

100

Neutrons

153

Mass number

253

Mass

253.1 ± 1.7 u

Mass excess

79.346 MeV

Spin

1/2+

Stability

Half-life: 3 days

Natural occurrence

Not found in nature

Decays to

• electron capture 88.0 % → Es-253
• alpha 12.0 % → Cf-249