¹⁷⁶Tl — Unstable · t½ ≈ 200 ms · Decay: β⁺ → ¹⁷⁶Hg · Type: synthetic · Uses: research.
¹⁷⁷Tl — Unstable · t½ ≈ 370 ms · Decay: β⁺ → ¹⁷⁷Hg · Type: synthetic · Uses: research.
¹⁷⁸Tl — Unstable · t½ ≈ 350 ms · Decay: β⁺ → ¹⁷⁸Hg · Type: synthetic · Uses: research.
¹⁷⁹Tl — Unstable · t½ ≈ 450 ms · Decay: β⁺ → ¹⁷⁹Hg · Type: synthetic · Uses: research.
¹⁸⁰Tl — Unstable · t½ ≈ 1.5 s · Decay: β⁺ → ¹⁸⁰Hg · Type: synthetic · Uses: research.
¹⁸¹Tl — Unstable · t½ ≈ 3.0 s · Decay: β⁺ → ¹⁸¹Hg · Type: synthetic · Uses: research.
¹⁸²Tl — Unstable · t½ ≈ 4.2 s · Decay: β⁺ → ¹⁸²Hg · Type: synthetic · Uses: research.
¹⁸³Tl — Unstable · t½ ≈ 5.0 s · Decay: β⁺ → ¹⁸³Hg · Type: synthetic · Uses: research.
¹⁸⁴Tl — Unstable · t½ ≈ 10.0 s · Decay: β⁺ → ¹⁸⁴Hg · Type: synthetic · Uses: research.
¹⁸⁵Tl — Unstable · t½ ≈ 9.0 s · Decay: β⁺ → ¹⁸⁵Hg · Type: synthetic · Uses: research.
¹⁸⁶Tl — Unstable · t½ ≈ 28.0 s · Decay: β⁺ → ¹⁸⁶Hg · Type: synthetic · Uses: research.
¹⁸⁷Tl — Unstable · t½ ≈ 23.0 s · Decay: β⁺ → ¹⁸⁷Hg · Type: synthetic · Uses: research.
¹⁸⁸Tl — Unstable · t½ ≈ 25.0 s · Decay: β⁺ → ¹⁸⁸Hg · Type: synthetic · Uses: research.
¹⁸⁹Tl — Unstable · t½ ≈ 2.0 min · Decay: β⁺ → ¹⁸⁹Hg · Type: synthetic · Uses: research.
¹⁹⁰Tl — Unstable · t½ ≈ 2.6 min · Decay: β⁺ → ¹⁹⁰Hg · Type: synthetic · Uses: research.
¹⁹¹Tl — Unstable · t½ ≈ 3.0 min · Decay: β⁺ → ¹⁹¹Hg · Type: synthetic · Uses: research.
¹⁹²Tl — Unstable · t½ ≈ 4.0 min · Decay: β⁺ → ¹⁹²Hg · Type: synthetic · Uses: research.
¹⁹³Tl — Unstable · t½ ≈ 4.0 min · Decay: β⁺ → ¹⁹³Hg · Type: synthetic · Uses: research.
¹⁹⁴Tl — Unstable · t½ ≈ 33.0 min · Decay: β⁺ → ¹⁹⁴Hg · Type: synthetic · Uses: research.
¹⁹⁵Tl — Unstable · t½ ≈ 1.2 h · Decay: β⁺ → ¹⁹⁵Hg · Type: synthetic · Uses: research.
¹⁹⁶Tl — Unstable · t½ ≈ 1.8 h · Decay: β⁺ → ¹⁹⁶Hg · Type: tracer · Uses: research.
¹⁹⁷Tl — Unstable · t½ ≈ 2.8 h · Decay: β⁻ → ¹⁹⁷Pb · Type: tracer · Uses: nuclear research.
¹⁹⁸Tl — Unstable · t½ ≈ 5.3 h · Decay: β⁻ → ¹⁹⁸Pb · Type: tracer · Uses: nuclear research.
¹⁹⁹Tl — Unstable · t½ ≈ 7.4 h · Decay: β⁻ → ¹⁹⁹Pb · Type: tracer · Uses: nuclear research.
²⁰⁰Tl — Unstable · t½ ≈ 26.1 h · Decay: β⁻ → ²⁰⁰Pb · Type: tracer · Uses: nuclear research.
²⁰¹Tl — Unstable · t½ ≈ 3.0 d · Decay: β⁻ → ²⁰¹Pb · Type: tracer · Uses: nuclear research.
²⁰²Tl — Unstable · t½ ≈ 12.2 d · Decay: β⁻ → ²⁰²Pb · Type: tracer · Uses: nuclear research.
²⁰³Tl — Unstable · t½ ≈ 1.9 d · Decay: β⁻ → ²⁰³Pb · Type: tracer · Uses: tracer studies.
²⁰⁴Tl — Unstable · t½ ≈ 3.8 y · Decay: β⁻ → ²⁰⁴Pb · Type: environmental tracer · Uses: geochemistry.
²⁰⁵Tl — Stable · — · Type: stable (primordial, ~70.5%) · Uses: isotope tracer, alloys, semiconductors.
²⁰⁶Tl — Unstable · t½ ≈ 4.2 min · Decay: β⁻ → ²⁰⁶Pb · Type: synthetic · Uses: research.
²⁰⁷Tl — Unstable · t½ ≈ 4.8 min · Decay: β⁻ → ²⁰⁷Pb · Type: synthetic · Uses: research.
²⁰⁸Tl — Unstable · t½ ≈ 3.1 min · Decay: β⁻ → ²⁰⁸Pb · Type: synthetic · Uses: research.
²⁰⁹Tl — Unstable · t½ ≈ 2.2 min · Decay: β⁻ → ²⁰⁹Pb · Type: synthetic · Uses: research.
²¹⁰Tl — Unstable · t½ ≈ 1.3 min · Decay: β⁻ → ²¹⁰Pb · Type: synthetic · Uses: tracer in nuclear physics.
²¹¹Tl — Unstable · t½ ≈ 76.0 s · Decay: β⁻ → ²¹¹Pb · Type: synthetic · Uses: research.
²¹²Tl — Unstable · t½ ≈ 30.0 s · Decay: β⁻ → ²¹²Pb · Type: synthetic · Uses: research.
²¹³Tl — Unstable · t½ ≈ 24.0 s · Decay: β⁻ → ²¹³Pb · Type: synthetic · Uses: research.
²¹⁴Tl — Unstable · t½ ≈ 11.0 s · Decay: β⁻ → ²¹⁴Pb · Type: synthetic · Uses: research.
²¹⁵Tl — Unstable · t½ ≈ 7.0 s · Decay: β⁻ → ²¹⁵Pb · Type: synthetic · Uses: research.
Thallium — isotope count: 40 total · Stable: 2 (²⁰³Tl, ²⁰⁵Tl) · Unstable: 38.
(Data: IAEA LiveChart, NUBASE2020, ENSDF; notable applications: ²⁰¹Tl in nuclear medicine (myocardial perfusion imaging), ²⁰³Tl/²⁰⁵Tl in geochemistry, ²⁰⁴Tl as environmental tracer.)
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