Isotopes of neptunium

<a href="/facts/Neptunium/pwp7Yvds">Neptunium</a> (93Np) is usually considered an <a href="/facts/Artificial_element/azU9Nr1m">artificial element</a>, although trace quantities are found in nature, so a <a href="/facts/Standard_atomic_weight/8arqbQsq">standard atomic weight</a> cannot be given. Like all trace or artificial elements, it has no <a href="/facts/Stable_isotopes/vgcdxgjA">stable isotopes</a>. The first <a href="/facts/Isotope/KD9B1y6o">isotope</a> to be synthesized and identified was 239Np in 1940, produced by bombarding <a href="/facts/Uranium-238/QhcHm6q8">238U</a> with <a href="/facts/Neutron/oRCM1geb">neutrons</a> to produce 239U, which then underwent <a href="/facts/Beta_decay/vxTBlckp">beta decay</a> to 239Np.
Trace quantities are found in nature from <a href="/facts/Neutron_capture/elsFpM12">neutron capture</a> reactions by <a href="/facts/Uranium/n2sGWBzU">uranium</a> atoms, a fact not discovered until 1951.
Twenty-five neptunium <a href="/facts/Radioisotope/5WpCfbdq">radioisotopes</a> have been characterized, with the most stable being 237Np with a <a href="/facts/Half-life/kGVH8BAB">half-life</a> of 2.14 million years, 236Np with a half-life of 154,000 years, and 235Np with a half-life of 396.1 days. All of the remaining <a href="/facts/Radioactive/Ya6FVjt4">radioactive</a> isotopes have half-lives that are less than 4.5 days, and the majority of these have half-lives that are less than 50 minutes. This element also has five <a href="/facts/Meta_state/L8DHcqnk">meta states</a>, with the most stable being 236mNp (t1/2 22.5 hours).
The isotopes of neptunium range from 219Np to 244Np, though the intermediate isotope 221Np has not yet been observed. The primary <a href="/facts/Decay_mode/Ya6FVjt4">decay mode</a> before the most stable isotope, 237Np, is <a href="/facts/Electron_capture/EIccoV1u">electron capture</a> (with a good deal of <a href="/facts/Alpha_emission/rCsHNIUE">alpha emission</a>), and the primary mode after is <a href="/facts/Beta_emission/vxTBlckp">beta emission</a>. The primary <a href="/facts/Decay_product/hT0obfLv">decay products</a> before 237Np are <a href="/facts/Isotopes_of_uranium/zWIQ6MVL">isotopes of uranium</a> and <a href="/facts/Isotopes_of_protactinium/AVGw4A8U">protactinium</a>, and the primary products after are <a href="/facts/Isotopes_of_plutonium/ASACBN4x">isotopes of plutonium</a>. Neptunium is the heaviest element for which the location of the <a href="/facts/Proton_drip_line/k3PfJUoy">proton drip line</a> is known; the lightest bound isotope is 220Np.

Isotopes of neptunium open-in-new

Isotopes of neptunium