text: an oxidation-reduction reaction involves the transfer of a(n)_________.? choose one: a) electron  b) water molecule  c) hydrogen ion  d)  oxygen molecule  e)carbon dioxide molecule. a) electron  electrons have a negative charge. if an electron is transferred to an atom...that atom is reduced. ex..fe 3+ (iron) plus 1 electron = fe 2+... the charge was reduced from 3 to 2. oxidation is just the opposite. when an electron is taken from an atom, the charge increases. ex... na (sodium) metal with a 0 charge loses an electron, it is oxidized to na 1+