Is it possible for a chemical to behave as an acid in one instance and as a base in another instance?

No, unless the chemical is altered in some sort of way, it should have the same acidity or baseness as it had before.

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.