How would you classify hydrogen and why?

Hydrogen is classified as a non-metal based on its
physical properties. Metals, located to the left of the stairstep elements, have the
properties of being shiny, conductive, malleable (can be made into sheets) and ductile
(can be made into wire). Since hydrogen has none of these properties it is obviously not
a metal.

It is located at the top of group one of the
periodic table because the periodic table is arranged so that all elements in a given
group have the same number of outer or valence electrons.  All elements in group one
have one valence electrons, as does hydrogen.

In terms of
its chemical reactions hydrogen can form both covalent and ionic bonds. It bonds
covalently with other non-metals such as nitrogen, sulfur, oxygen, carbon, etc.  In
fact, there are more chemical compounds which contain hydrogen and carbon (hydrocarbons)
than all other chemical compounds combined.

It forms ionic
bonds in acid solutions such as hydrochloric acid, nitric acid, sulfuric acid, etc. in
which it exists as a positive ion and determines the pH of those
solutions.

Hydrogen is also unique in that it can form
chemical compounds in which it has an ionic charge of -1.  Examples are the metal
hydrides such as LiH, NaH, etc.

Hydrogen has three primary
isotopes, H-1 (protium), H-2 (deuterium), and H-3 (tritium), with H-1 being the most
common and abundant element in the universe.

H-2 is used in
nuclear applications (see link) and H-3 is a radioactive isotope that once was painted
on the hands watches so they would glow in the dark and be visible at
night.