Nuclear Labdigital resource

Chains of decay

A radioactive nucleus rarely ends at its first daughter — that daughter decays in turn, and so on for a dozen steps. Each chain below lists every decay in order, with the energy it releases and how long each step takes.

Starts in uranium ore and ends at stable lead-206. This is the chain that puts radon gas in basements.

steps
14
alpha / beta
8 α · 6 β
energy released
51.8 MeV
ends at
Lead-206
  • 1
    U-238Th-234
    α AlphaZ − 2 · A − 4
    4.270 MeV
    4.47 billion years
  • 2
    Th-234Pa-234
    β⁻ Beta-minusZ + 1 · A unchanged
    0.273 MeV
    24.1 days
  • 3
    Pa-234U-234
    β⁻ Beta-minusZ + 1 · A unchanged
    2.290 MeV
    1.17 minutes
  • 4
    U-234Th-230
    α AlphaZ − 2 · A − 4
    4.859 MeV
    245,500 years
  • 5
    Th-230Ra-226
    α AlphaZ − 2 · A − 4
    4.770 MeV
    75,400 years
  • 6
    Ra-226Rn-222
    α AlphaZ − 2 · A − 4
    4.871 MeV
    1,600 years
  • 7
    Rn-222Po-218
    α AlphaZ − 2 · A − 4
    5.590 MeV
    3.82 days
  • 8
    Po-218Pb-214
    α AlphaZ − 2 · A − 4
    6.115 MeV
    3.1 minutes
  • 9
    Pb-214Bi-214
    β⁻ Beta-minusZ + 1 · A unchanged
    1.024 MeV
    26.8 minutes
  • 10
    Bi-214Po-214
    β⁻ Beta-minusZ + 1 · A unchanged
    3.272 MeV
    19.9 minutes
  • 11
    Po-214Pb-210
    α AlphaZ − 2 · A − 4
    7.834 MeV
    164 microseconds
  • 12
    Pb-210Bi-210
    β⁻ Beta-minusZ + 1 · A unchanged
    0.064 MeV
    22.3 years
  • 13
    Bi-210Po-210
    β⁻ Beta-minusZ + 1 · A unchanged
    1.163 MeV
    5.01 days
  • 14
    Po-210Pb-206
    α AlphaZ − 2 · A − 4
    5.407 MeV
    138.4 days

why the chain steps the way it does

An alpha step removes two protons and two neutrons, so the mass number falls by 4 and the atomic number by 2 — a jump down the periodic table, usually into a different element.

A beta step leaves the mass number alone and turns a neutron into a proton, moving one place to the right. Alpha steps repeat until the nucleus is light enough to stop.