Helium is naturally nonreactive due to the low number of electrons in its Valence
Helium is naturally a gas. Helium is also unstable because the valence isn't full.
The Great Divide
The periodic Table is split by a line that is near the right of the table. The line splits the metals and the non-metals, it also has metalloids along the line. since Helium is on the right of the line it is a non metal.