²⁰⁹Th — Unstable · t½ ≈ 7.8 ms · Decay: α → ²⁰⁵Ra · Type: synthetic · Uses: research.
²¹⁰Th — Unstable · t½ ≈ 30.0 ms · Decay: α → ²⁰⁶Ra · Type: synthetic · Uses: research.
²¹¹Th — Unstable · t½ ≈ 40.0 ms · Decay: α → ²⁰⁷Ra · Type: synthetic · Uses: research.
²¹²Th — Unstable · t½ ≈ 30.0 ms · Decay: α → ²⁰⁸Ra · Type: synthetic · Uses: research.
²¹³Th — Unstable · t½ ≈ 144 ms · Decay: α → ²⁰⁹Ra · Type: synthetic · Uses: research.
²¹⁴Th — Unstable · t½ ≈ 0.9 s · Decay: β⁺ → ²¹⁴Ac · Type: synthetic · Uses: research.
²¹⁵Th — Unstable · t½ ≈ 1.0 s · Decay: β⁺ → ²¹⁵Ac · Type: synthetic · Uses: research.
²¹⁶Th — Unstable · t½ ≈ 26.0 s · Decay: β⁺ → ²¹⁶Ac · Type: synthetic · Uses: research.
²¹⁷Th — Unstable · t½ ≈ 0.2 s · Decay: α → ²¹³Ra · Type: synthetic · Uses: research.
²¹⁸Th — Unstable · t½ ≈ 117 ns · Decay: α → ²¹⁴Ra · Type: synthetic · Uses: research.
²¹⁹Th — Unstable · t½ ≈ 1.05 μs · Decay: α → ²¹⁵Ra · Type: synthetic · Uses: research.
²²⁰Th — Unstable · t½ ≈ 9.7 μs · Decay: α → ²¹⁶Ra · Type: synthetic · Uses: research.
²²¹Th — Unstable · t½ ≈ 1.7 ms · Decay: α → ²¹⁷Ra · Type: synthetic · Uses: research.
²²²Th — Unstable · t½ ≈ 2.2 ms · Decay: α → ²¹⁸Ra · Type: synthetic · Uses: research.
²²³Th — Unstable · t½ ≈ 0.6 ms · Decay: α → ²¹⁹Ra · Type: synthetic · Uses: research.
²²⁴Th — Unstable · t½ ≈ 1.05 d · Decay: α → ²²⁰Ra · Type: natural (Thorium series) · Uses: tracer.
²²⁵Th — Unstable · t½ ≈ 8.7 min · Decay: α → ²²¹Ra · Type: synthetic · Uses: research.
²²⁶Th — Unstable · t½ ≈ 30.6 min · Decay: α → ²²²Ra · Type: synthetic · Uses: research.
²²⁷Th — Unstable · t½ ≈ 18.7 d · Decay: α → ²²³Ra · Type: natural (Actinium series) · Uses: tracer.
²²⁸Th — Unstable · t½ ≈ 1.91 y · Decay: α → ²²⁴Ra · Type: natural (Thorium series) · Uses: radiometric dating.
²²⁹Th — Unstable · t½ ≈ 7.3×10³ y · Decay: α → ²²⁵Ra · Type: long-lived radionuclide · Uses: nuclear clock research.
²³⁰Th — Unstable · t½ ≈ 7.54×10⁴ y · Decay: α → ²²⁶Ra · Type: long-lived radionuclide · Uses: geochronology.
²³¹Th — Unstable · t½ ≈ 25.5 h · Decay: β⁻ → ²³¹Pa · Type: synthetic · Uses: research.
²³²Th — Unstable · t½ ≈ 1.4×10¹⁰ y · Decay: α → ²²⁸Ra · Type: primordial radionuclide · Uses: fertile fuel for breeder reactors.
²³³Th — Unstable · t½ ≈ 22.3 min · Decay: β⁻ → ²³³Pa · Type: synthetic · Uses: nuclear fuel cycle.
²³⁴Th — Unstable · t½ ≈ 24.1 d · Decay: β⁻ → ²³⁴Pa · Type: natural (Uranium series) · Uses: tracer.
²³⁵Th — Unstable · t½ ≈ 7.2 min · Decay: β⁻ → ²³⁵Pa · Type: synthetic · Uses: research.
²³⁶Th — Unstable · t½ ≈ 37.5 min · Decay: β⁻ → ²³⁶Pa · Type: synthetic · Uses: research.
²³⁷Th — Unstable · t½ ≈ 4.8 min · Decay: β⁻ → ²³⁷Pa · Type: synthetic · Uses: research.
²³⁸Th — Unstable · t½ ≈ 9.4 min · Decay: β⁻ → ²³⁸Pa · Type: synthetic · Uses: research.
Thorium — isotope count: 30 total · Stable: none · Unstable: 30.
(Data: IAEA LiveChart, NUBASE2020, ENSDF; notable applications: ²³²Th as fertile fuel in breeder and molten salt reactors, ²²⁸Th and ²³⁰Th in geochronology, ²²⁹Th in nuclear clock development.)
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