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Redox reactions can entail proton transfers and other bond-breaking and bond-making activities in addition to electron transfers, the equations describing them are far more complicated than those explaining acid-base reactions.
We need a system for keeping precise track of all the electrons in order to spot redox processes. Before and after the reaction, oxidation numbers are assigned to each atom.
In NO3– for example, the nitrogen has an oxidation number of +5, while each oxygen has an oxidation number of –2. The nitrogen has lost its initial five valence electrons to the electronegative oxygens, resulting in this arbitrary assignment.
The nitrogen in NO2, on the other hand, has an oxidation number of + 4 and can be considered of as having one valence electron for itself, one more than it had in NO3–.
This arbitrary one-electron gain corresponds to a nitrogen atom decrease while going from NO3– to NO2. In general, reduction is defined as a decrease in the oxidation number of an atom. Oxidation is the process of increasing an atom’s oxidation number.
Oxidation numbers, while important and necessary for distinguishing redox reactions, are a very artificial instrument. In NO3– the nitrogen atom does not have a true +5 charge, which can be lowered to +4 in NO2. Instead, covalent connections and electron-pair sharing exist between nitrogen and oxygen in both species, and nitrogen’s valence electrons have not been completely lost to oxygen.
Despite the fact that this may (and should) make you doubt the veracity of oxidation numbers, they are an invaluable tool for detecting electron-transfer activities. Their use is perfectly legitimate as long as they are utilised for that reason solely and not to imply that atoms in covalent species have the enormous charges that oxidation numbers frequently imply.
Molecular Redox
Redox Reactions at the Molecular Level
In a reaction that produces ions, the electron loss and gain is easily visible. In many processes, however, no such electron transfer takes place.
A covalent bond is a sort of link in which electrons are shared between atoms in a chemical complex. Even so, reactions involving molecular compounds are frequently classed as redox reactions.
When hydrogen gas is combined with oxygen gas, the result is water.
A pair of bonding electrons is shared equally among the hydrogen atoms in each unique hydrogen molecule (a non polar covalent bond). Similarly, the oxygen molecule’s bonding electrons are split equally between the two oxygen atoms.
The electron sharing is no longer equal when the atoms are rearranged to form the water molecule. The bonding electrons in each hydrogen-oxygen link in the water molecule are more attracted to the oxygen atom than to the hydrogen atom. Because oxygen has a higher electronegativity than hydrogen, we know this.
Water is extremely polar, despite the fact that hydrogen and oxygen are nonpolar.
Electrons in hydrogen, oxygen, and water are bonded together.
Conclusion
Returning to our prior definitions of oxidation as the gain of oxygen or loss of hydrogen and reduction as the gain of hydrogen or loss of oxygen is another way to address this type of problem. This simplifies the decision-making process when it comes to redox reactions. Because it incorporates oxygen to produce water, the hydrogen is oxidised. The oxygen, on the other hand, is reduced as a result of the addition of hydrogen to produce water.
