SOLUTION. Step 1: Draw the Lewis Structure & Resonance. Step 2: Combine the resonance structures by adding (dotted) bonds where other resonance bonds can be formed. Step 3: Add only the lone pairs found on ALL resonance structures.
Draw the Lewis Structure & Resonance for the molecule (using solid lines for bonds). Where there can be a double or triple bond, draw a dotted line (-----) for the bond. Draw only the lone pairs found in all resonance structures, do not include the lone pairs that are not on all of the resonance structures.
When drawing a resonance structure there are three rules that need to be followed for the structures to be correct: Only electrons move and the nuclei of the atoms never move. Only electrons that can move are pi electrons, single unpaired electrons, and lone pair electrons.
Rules to remember for recognising resonance structures:
Atoms never move. You can only move electrons in π bonds or lone pairs (that are in p orbitals) The overall charge of the system must remain the same. The bonding framework of a molecule must remain intact.
Drawing the Resonance Structure
To find the formal charges, count the number of electrons the atom owns and compare it to its valence electrons. For example, the top oxygen owns 5 electrons. 2 of the electrons are a lone pair and the other 3 come from the bonds. Remember, it owns only one of the electrons in a bond.
Rule #1: Neutral Resonance Structures Are More “Important” Than Charged Resonance Structures. Resonance forms become less significant as the number of charges are increased (see earlier post).
Resonance structures tell us how the electrons are distributed throughout the system. In order to know how the molecule actually is in real life, we have to know all the major resonance structures, as they all contribute to the resonance hybrid structure.
The benzene ring has two resonance structures which can be drawn by moving elections in a cyclic manner. Conjugated double bonds contain multiple resonance structures.
Definition. Resonance Effect – The polarity induced in a molecule by the interaction of a lone pair of electrons with a pi bond or the interaction of two pi bonds in nearby atoms is known as the resonance effect.
(I) H2C−−N+≡N. (II) H2C=N+ = N−
Stability of resonating structures is directly proportional to the number of covalent bonds. In structure I, there are more covalents bonds than in structure II, also resonating structure with no charges is the most stable one. Therefore, structure I is more stable than II.
Resonance is a phenomenon that occurs when the matching vibrations of another object increase the amplitude of an object's oscillations.
Understanding resonance is essential for solving problems of increased vibration. Resonance is a condition that can occur in mechanical structures and can be described as sensitivity to a certain vibration frequency. Resonance occurs when a natural frequency is at or close to a forcing frequency, such as rotor speed.