OK so we have a dipolar bond between two elements. This bond makes the other electrons redistribute in order to rest in peace. Everything's OK up until now. What happens, however, when two of these other electrons have the same spin an yet they end up together because of this redistribution? I have been told that the spin of one of them changes (that is, from 1/2 to -1/2 or the other way around). Is that true? And if it is, how does that happen?