Not sure about rubidum, but rubidium is a metal.
Zodarion rubidum was created in 1914.
This alkali metal is Rubidium Rb, having atomic no 37
37
Neon is a non-metal. It is one of the Noble Gasses which are all non-metals.
Non metal
Oxygon is a non-metal
Non metal
non-metal
non-metal
Non-metal
non metal
non metal