Question

Both Helium and beryllium have two electrons in the valence shell. He is a noble gas where is beryllium is a metal. justify

Answer 1

helium is noble gas because it has only 2 electron which occupy ist orbit
hence its octat is complete
in first shell octat ie completed by 2 electron in 2nd shell octat is completed by 8 electron and so on
beryllium is in group 2 which is the group of alkaline earth metal.
and metallic character is decreased along the period left to right

Answer 2

simply helium have only two electron and they are closely attached by nucleus , not show exited state .