Which one of the following is NOT a resonance structure for NO21−? O with a pair of electrons above and below, a double-bond to the N with a pair of electrons above, a single-bond to the O with three pairs of electrons around it. The whole thing is labeled with a -1. O with a pair of electrons above and below, a double-bond to the N with a pair of electrons above, a double-bond to the O with two pairs of electrons around it. The whole thing is labeled with a -1. O with three pairs of electrons around it, a single-bond to the N with a pair of electrons above, a double-bond to the O with two pairs of electrons. The whole thing is labeled with a -1. All of the above are resonance structures for NO21−.