You should never heat chemicals in a closed system (closed bottle or flask) because

You should never heat chemicals in a closed system (closed bottle or flask) because it might explode.

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.