Helium chemical symbol

helium, chemical, element, gas, atom, inert, noble, nonreactive, atmosphere, rare, periodic, group, atomic, number, mass, density, solubility, pressure, cryogenic, cooling, superfluid, plasma, ionization, excitation, spectrum, stability, bonding, electron, nuclear, fusion, energy, insulation, balloon, lifting, leakdetection, industry, laboratory, environment, safety, molecules, chemicalprocess, gaseous