Helium is the second element of the periodic table. It usually (99.99% of the time) has 2 protons, 2 neutrons and 2 electrons. Since it's 2 electrons completely fill it's 1s-orbital, helium is a noble (or inert) gas, meaning that it rarely reacts with other elements. Helium was discovered in 1870 through spectrographic analysis. Since it is lighter than air, specs of helium quickly float off into outer space.