The ion of one isotope of nickel (Ni) has 27 electrons and a mass number of 58. How many neutrons does the ion have, and what is the ionic charge?
a) Neutrons: 31, Ionic charge: +1
b) Neutrons: 31, Ionic charge: -1
c) Neutrons: 31, Ionic charge: +2
d) Neutrons: 31, Ionic charge: -2