🚀 go-pugleaf

My courses in modern physics and electronics were several years ago,
so I might be a little rusty here, but ..

Hydrogen, under ordinary conditions of temperature and pressure is
a non-conductor of electricity. It is only under special conditions,
when the gas becomes plasma that it can conduct electricity.

Your instructor's 'rule' that elements with 1 or 2 valence electrons
are conductors, etc. is a little too simplistic, as the Hydrogen 
example itself proves. 

What is needed for matter to conduct electricity is the presence of
either free electrons (as in metals and semiconductors) or ions (as in
conducting liquids and plasma). Essentially, what this means is that
in order to conduct, electrons in individual the atoms that make up the
substance need to have sufficient energy to pull away from their orbits
and move freely about the substance, so that when an electric voltage
is applied, a current can be produced.

If the amount of energy needed is available at room temperature
the substance will conduct at room temperature. The energy needed 
depends on a lot of factors other than temperature - molecular 
structure, atomic number, state (solid/liquid/gas) etc. In summary,
conductivity of an element depends on the energy needed for the outer
electrons to become free, not necessarily on the valency.