I think it would be one as the total charge since the protons and neutrons cancel out each other, leaving one neutron. The other option is that it totals out causeing their to be a larger charge which would be 7.
The mass number is the total amount of protons and neutrons in an atom. Therefore, if there are 8 protons and 10 neutrons, the mass number is 18 (8 + 10 = 18).
