Atomic number: 2

Symbol: He

Category: non-metal, noble gas

Density at 25°Cgas 

Helium is a little more familiar to us in the modern world. Helium balloons for example are filled with mixture of air and helium. It's also found in some florescent lighting systems. Usually having 2 protons locked together with 2 electrons makes it very stable and very non reactive. 


Helium gas electrically excited. image: wikipedia

Use, natural applications or common combinations: 

  • constituents of stars and nebula, gas giant planets
  • party balloons, lights

Basic characteristics:

  • Standard atomic weight: 4.002602(2)
  • Melting/freezing point: −272.20 °C (special pressures)
  • Boiling point: −268.93 °C
  • Radioactivity: all stable 4He most common