Oxygen has an atomic number of 8. in order to fill its outer electron shell, how many electrons does it need?

Oxygen has 8 electrons. On the outer ring, it has 6 valance electrons. It need 2 more valance electrons to be stable.

Because electrons have negligible mass, to account for the mass of the isotope, there must be 16 neutrons, 16 neutrally charged, massive, fundamental particles present in the sulfur nucleus. and thus finally, if we have the 32s2− ion, there are 18 electrons, 16 protons, and 16 neutrons.

The answer is a) carbon-12