Neptunium-239
= Neptunium-239
{title2=$^{239}_{93}\mathrm{Np}$}
<Neptunium-239> is a radioactive isotope with ninety-three protons and one hundred forty-six neutrons. It beta-decays to plutonium-239.
It occurs in the sequence following neutron capture by uranium-238 and beta decay of uranium-239. This is an example of transmutation changing the chemical element through a nuclear process, unlike an ordinary chemical reaction that rearranges electrons and bonds.