Atoms like carbon and nitrogen do not form ions because the electronegativity of these atoms are not that high nor very low which means electrons are fairly stable in the atom. While chlorine has very high electronegativity and for sodium very low, atoms tend to receive or release electrons.
Atomic mass= number of protons + number of neutrons

hope this helps
In salty water ions are produced by the salt
here salt is NaCl
so it will break in Na⁺ and Cl⁻
They carry the current
Na⁺ moves towards cathode and Cl⁻ moves towards anode
So current is carrying by ions which are Na⁺ and Cl⁻