EXPLAIN RESONANCE IN DETAIL?
Answers
Answer:
In chemistry, resonance, also called mesomerism, is a way of describing bonding in certain molecules or ions by the combination of several contributing structures (or forms, also variously known as resonance structures or canonical structures) into a resonance hybrid (or hybrid structure) in valence bond theory.
Explanation:
Resonance Structures?
Resonance structures are sets of Lewis structures that describe the delocalization of electrons in a polyatomic ion or a molecule.
In many cases, a single Lewis structure fails to explain the bonding in a molecule/polyatomic ion due to the presence of partial charges and fractional bonds in it. In such cases, resonance structures are used to describe chemical bonding.
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Resonance in chemistry could be a manner of describing the bonding in particular molecules or ions by merging many contributory structures or forms, jointly called canonical structures or resonance structures within the theory of valence bonding into a hybrid resonance (or hybrid structure).
Resonance Structures
The different resonance structures of the carbonate ion (CO32-) are illustrated above. The delocalization of electrons is described via fractional bonds (which are denoted by dotted lines) and fractional charges in a resonance hybrid.
Sometimes resonance structures are not equivalent, and it is important to determine which one(s) best describe the actual bonding. Formal charge can be used to predict which resonance structures are favoured.
Resonance Structures of NO2– Ion
In the nitrite ion, the bond lengths of both nitrogen-oxygen bonds are equal. The Lewis dot structures of NO2– highlight a difference in the bond order of the two N-O bonds. The resonance hybrid of this polyatomic ion, obtained from its different resonance structures, can be used to explain the equal bond lengths, as illustrated below.
Resonance Structures of NO2
The resonance hybrid of NO2– suggests that each oxygen atom holds a partial charge of magnitude -½. The bond length of the N-O bonds is found to be 125 pm.
Resonance Structures of NO3– Ion
Nitrogen is the central atom in a nitrate ion. It is singly bonded to two oxygen atoms and doubly bonded to one oxygen atom. The oxygen atoms that are singly bonded to the nitrogen hold a charge of -1 (in order to satisfy the octet configuration). The central nitrogen atom has a charge of +1 and the overall charge on the nitrate ion is -1. The three possible resonance structures of NO3– are illustrated below.
Resonance Structures of NO3– Ion
If a resonance hybrid of this polyatomic ion is drawn from the set of Lewis structures provided above, the partial charge on each oxygen atom will be equal to -(⅔). The net charge on the central atom remains +1. This resonance hybrid is illustrated below.
Resonance Structures of NO3
Resonance Structures of O3
The ozone (O3) molecule consists of a central oxygen atom which is singly bonded to one oxygen atom and doubly bonded to another. There is no net charge on this molecule, but the Lewis structures of this molecule show a +1 charge on the central oxygen and a -1 charge on the singly bonded oxygen. The two resonance structures of the ozone molecule are illustrated below.