Atomic mass: 4.002602 g/mol
Helium is element number 2 in the Periodic Table. Helium is a noble gas and is used in liquid form as a cooling agent in laboratories and as a packaging gas in the production of food (E-number E 939). Alpha-particles is helium nuclei without electrons i.e. He2+ naked helium nuclei. Alpha particles is produced by radioactive decay of e.g. radium. As a noble gas helium rarely undergo chemical reactions with other elements, the gas is therefore single-atomic in contrast to e.g. nitrogen or oxygen gases which are diatomic.
MP= -272.2 o C; BP= -268.93 o C; CAS-number: 7440-59-7;