Resonance structures have connectivity of atoms and distribution of electrons.

Resonance structures have same    connectivity of atoms and differ only in distribution of electrons.

Explanation:

Atoms supply the electrons from their outer electron shells. Electrons are found free in nature and are grouped around the nucleus into shells. Electrons can be further explained as negatively charged subatomic particle. Electrons have properties of both particles and waves and they can be moved around.

Resonance structures are imaginary structures and not all of them are created equally. Resonance structures have two or more possible electron structures, and, the resonance structures for a particular substance sometimes have different energy and stability. When resonance structures are identical, they are important descriptions  of the molecule. The position of the atoms is the same in the various resonance structures of a compound, but the electrons are distributed differently around the structure.

d) the number of neutrons plus the number of protons