Caesium-129 (Cs-129)

Identity

Protons

55

Neutrons

74

Mass number

129

Mass

128.9 ± 4.9 u

Mass excess

-87.499 MeV

Spin

1/2+*

Stability

Half-life: 1.34 days

Natural occurrence

Not found in nature

Decays to

• positron emission → Xe-129