Last question ! i don’t really understand

Select all of the statements which are true. electrons are located in shells or orbits around the atom. electrons orbit slowly around the atom. electrons travel in one flat path around the nucleus of an atom. the valence of an atom is determined by the number of electrons in the atom's outermost shell.

Which metals are called noble metals

Ahelium balloon contains 16.9 l of helium at stp. how many atoms of helium are in the balloon