What is the chemical formula for helium gas?

Helium is a noble gas and has the chemical symbol He. Helium is commonly known for its property of being lighter than air.

Helium is most commonly a gas, except for in extreme conditions. It has the atomic number 2, melts at -272 degrees Celsius and boils at -269 C. Helium is used in balloons because it is lighter than air and will make whichever container it is in float if the container itself is light enough. Helium is most commonly found in abundance in the atmosphere, but is also found in natural gas deposits below the surface of the Earth.