Helium - Definition - Law Dictionary Home Dictionary Definition helium

Definition :

An inert monoatomic gaseous element occurring in the atmosphere of the sun and stars and in small quantities in the earths atmosphere in several minerals and in certain mineral waters It is obtained from natural gas in industrial quantities Symbol He atomic number 2 at wt 40026 C12011 Helium was first detected spectroscopically in the sun by Lockyer in 1868 it was first prepared by Ramsay in 1895 Helium has a density of 198 compared with hydrogen and is more difficult to liquefy than the latter Chemically it is an inert noble gas belonging to the argon group and cannot be made to form compounds The helium nucleus is the charged particle which constitutes alpha rays and helium is therefore formed as a decomposition product of certain radioactive substances such as radium The normal helium nucleus has two protons and two neutrons but an isotope with only one neutron is also observed in atmospheric helium at an abundance of 0013 Liquid helium has a boiling point of 2689deg C at atmospheric pressure and is used for maintaining very low temperatures both in laboratory experimentation and in commercial applications to maintain superconductivity in low temperature superconducting devices Gaseous helium at normal temperatures is used for buoyancy in blimps dirigibles and high altitude balloons and also for amusement in party balloons