Neither the mass alone nor the charge alone tells you what element the atom's nucleus is.
The only charged particles in the nucleus are the protons, which are positively charged. So every atom has a positively charged nucleus. The <em>NUMBER of protons in the nucleus</em> is the unique thing about each element.
It's not the mass, because there are also neutrons in the nucleus. A neutron has the same mass as a proton has, but no charge. AND, just to make it a little more complicated, every element can have atoms with a few <u><em>different</em></u> numbers of neutrons in the nucleus, so atoms of that element can have a few different masses. (These are called "isotopes" of that element.)
Bottom line:
-- The element is identified by the number of protons in the nucleus.
-- The nuclear charge is positive (that number), and
-- The nuclear mass is (that number) + (the number of neutrons in it).