Predict the ground-state electron configuration of the following ions. write your answers in abbreviated form, that is, beginning with a noble gas in brackets.
a). cr2+
b.)cu2+
c.)co3+

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.

Copper, silver, aluminum, cobalt, chromium, mercury 

They can measure  the amount of energy gained or lost