²²⁵Np — Unstable · t½ ≈ 2.3 min · Decay: β⁺ → ²²⁵U · Type: synthetic · Uses: research.
²²⁶Np — Unstable · t½ ≈ 29.0 s · Decay: β⁺ → ²²⁶U · Type: synthetic · Uses: research.
²²⁷Np — Unstable · t½ ≈ 2.3 min · Decay: α → ²²³Pa · Type: synthetic · Uses: research.
²²⁸Np — Unstable · t½ ≈ 61.0 s · Decay: β⁺ → ²²⁸U · Type: synthetic · Uses: research.
²²⁹Np — Unstable · t½ ≈ 4.0 min · Decay: β⁺ → ²²⁹U · Type: synthetic · Uses: research.
²³⁰Np — Unstable · t½ ≈ 4.0 min · Decay: β⁺ → ²³⁰U · Type: synthetic · Uses: research.
²³¹Np — Unstable · t½ ≈ 2.6 min · Decay: β⁺ → ²³¹U · Type: synthetic · Uses: research.
²³²Np — Unstable · t½ ≈ 14.7 min · Decay: β⁺ → ²³²U · Type: synthetic · Uses: research.
²³³Np — Unstable · t½ ≈ 36.2 min · Decay: β⁻ → ²³³Pu · Type: nuclear cycle intermediate · Uses: thorium fuel cycle research.
²³⁴Np — Unstable · t½ ≈ 4.4 d · Decay: β⁻ → ²³⁴Pu · Type: synthetic · Uses: research.
²³⁵Np — Unstable · t½ ≈ 396 d · Decay: β⁻ → ²³⁵Pu · Type: synthetic · Uses: research.
²³⁶Np — Unstable · t½ ≈ 154×10³ y · Decay: α → ²³²Pa · Type: long-lived radionuclide · Uses: tracer in nuclear waste.
²³⁷Np — Unstable · t½ ≈ 2.14×10⁶ y · Decay: α → ²³³Pa · Type: long-lived radionuclide · Uses: nuclear fuel cycle, RTGs.
²³⁸Np — Unstable · t½ ≈ 2.12 d · Decay: β⁻ → ²³⁸Pu · Type: activation product · Uses: reactor research.
²³⁹Np — Unstable · t½ ≈ 2.356 d · Decay: β⁻ → ²³⁹Pu · Type: reactor intermediate · Uses: plutonium production.
²⁴⁰Np — Unstable · t½ ≈ 61.9 min · Decay: β⁻ → ²⁴⁰Pu · Type: synthetic · Uses: research.
²⁴¹Np — Unstable · t½ ≈ 14.7 min · Decay: β⁻ → ²⁴¹Pu · Type: synthetic · Uses: research.
²⁴²Np — Unstable · t½ ≈ 2.2 min · Decay: β⁻ → ²⁴²Pu · Type: synthetic · Uses: research.
²⁴³Np — Unstable · t½ ≈ 1.8 min · Decay: β⁻ → ²⁴³Pu · Type: synthetic · Uses: research.
²⁴⁴Np — Unstable · t½ ≈ 2.3 min · Decay: β⁻ → ²⁴⁴Pu · Type: synthetic · Uses: research.
Neptunium — isotope count: 20 total · Stable: none · Unstable: 20.
(Data: IAEA LiveChart, NUBASE2020, ENSDF, Wikipedia “Isotopes of neptunium.” Notable uses: ²³⁷Np in nuclear waste management, RTGs; ²³⁹Np as a key intermediate in Pu-239 production.)