Posted by ROSHAN B.S on Aug. 25, 2014, 7:23 p.m.
Helium-4 (4
2He or 4He) is a non-radioactive isotope of the element helium. It is by far the most abundant of the two naturally occurring isotopes of helium, making up about 99.99986% of the helium on Earth. Its nucleus is identical to an alpha particle, and consists of two protons and two neutrons.