**Question:**Which of the following are *not related* as resonance structures?**Options:**(A) Two molecular structures are shown. The first structure is a carbonyl group (C=O), with the carbon atom attached to a nitrogen atom (NH) with a negative charge. In the second structure, the carbon is bonded to an alcohol group (OH) and a neutral nitrogen atom (NH).(B) Two molecular structures are shown. The first structure is a carbonyl group (C=O), with the carbon atom attached to a hydroxyl group (OH). The second structure shows a carbonyl group with a separate hydroxyl group and an overall positive charge on the oxygen with the hydroxyl group, and a negative charge on the carbonyl oxygen.(C) Two molecular structures are shown. The first structure is a carbonyl group with a methylene group (CH2) attached, which carries a negative charge. The second structure shows a negatively charged oxygen double-bonded to a carbon atom.(D) Two molecular structures are shown. The first structure is a carbonyl group with a negative charge on the oxygen atom. In the second structure, the carbon is double-bonded to a neutral oxygen atom.**Analysis:**To determine which of these pairs are not resonance structures, it is important to recognize that resonance structures differ only in the position of electrons, not in the position of atoms. Both structures in a pair must have the same number of atoms bonded in the same way and should only differ in the position of electrons.

Resonance structure:If the Lewis structure of a molecule or ion cannot explain by a single structure then more than one Lewis structure is written, these Lewis structures are different by the position of the lone pair of electrons and the pi bond. These structures are called resonance structures. The position of the atoms does not change in all the resonance structures.The movement of pi electrons in resonance structures is shown by the curved arrow. For the given options three structures are resonance structures and these are as follows:The first structure is not a resonance structure, because an extra hydrogen atom is attached to the oxygen atom. This is an acid-base reaction and a proton is attached with the first structure.The right option is as follows: