Neptunium
Symbol Np, a radioactive metallic transuranic element which belongs to the actinoids; a.n. 93; r.a.m. 237.0482. The most stable isotope, neptunium-237, is having half-life of 2.2 +106 years and is produced in small quantities as a by product by nuclear reactors Other isotopes are having mass numbers 229.236 and 238-241. The only other relatively long-lived isotope is neptunium-236 (half-life 5x 103 years). the element was first produced by McMillan and Abelson in 1940.

Neutrino
An elementary particle with-out charge nd with spin ½, postulated by Pauli to account for the conservation of angular momentum in nuclear transformations. Neutrinos appear to have variable finite mass and to oscillate from one type to another.

Neutron
One of the fundamental particles in an atom. It has same mass as a proton but is electrically neutral