Helium is heavier than hydrogen but lighter than air, properties that make it popular for use in inflating party balloons. It also has the added advantage over hydrogen in that it doesn't burn. After hydrogen, helium is the simplest atom. It consists of two electrons orbiting a nucleus made up of two protons and neutrons.
Helium is inert and has no role in the body. However, it's widely used in cryogenics and in medical technologies such as MRIs. Other uses for helium include arc welding and the production of silicon wafers.
Helium's atomic number is 2. It has an atomic weight of about 4, a melting point of minus 457.96 degrees Fahrenheit, and a boiling point of minus 452.070 degrees F.
Helium is second only to hydrogen in abundance, but it is rare on Earth because it is so light that it easily escapes the Earth's atmosphere. Indeed, it got its name from the Greek sun god Helios because it was first discovered in the sun. The helium found on Earth is most often a result of the radioactive decay of uranium and thorium.Learn more about Atoms & Molecules