Uranium-231 (U-231)

Identity

Protons

92

Neutrons

139

Mass number

231

Mass

231.0 ± 2.9 u

Mass excess

33.806 MeV

Spin

5/2+#

Stability

Half-life: 4.2 days

Natural occurrence

Not found in nature

Decays to

• electron capture 100.0 % → Pa-231
• alpha 0.0040 % → Th-227