Question

why cannot we use water or air as conductor

Answer 1

water don't have valence electrons.

Answer 2

pure water is not a conductor because it does not have any empty orbits or unpaired electrons

Answer 3

I guess a conductor should have lots of free electrons or lots of ions. Pure water has very less ions. Almost 1 out of 10\(^{7}\) water molecules is in the form of dissociated H+ and OH- ions. Same is the case with air which also has very few free electrons and ions. So, they are insulators and not conductors.