Oxidation and reduction are very important chemical reactions that take place in our surroundings all the time. When a covalent compound loses electronics, it becomes more positively charged, and the process is called oxidation. Reduction is the opposite of oxidation, as during the process, a compound gains electronics and becomes more negatively charged. Reduction and oxidation are more commonly known as redox reactions, as the transfer of electrons takes place between chemical species (one loss and one gain).
- Oxidation involves the loss of electrons or an increase in the oxidation state, while reduction involves the gain of electrons or a decrease in the oxidation state.
- Oxidizing agents accept electrons and become reduced, whereas reducing agents donate electrons and become oxidized.
- Oxidation and reduction reactions always coincide, forming redox reactions.
Oxidation vs Reduction
Oxidation is the chemical reaction that takes place when a molecule or an atom becomes more positively charged when it loses single or multiple electrons. Reduction is a chemical reaction that happens when an atom or a molecule loses electrons, causing it to become negatively charged.
Oxidation is a chemical reaction where an atom or a molecule of a chemical species loses electrons (one or more) and becomes more positively charged. This chemical reaction increases the oxidation state and oxidation number of the chemical species that is undergoing oxidation. Oxygen is not always involved in the process of oxidation, but sometimes it can cause the species to lose electrons.
Reduction is a chemical reaction where an atom or a molecule of a chemical species gains electrons (one or more) and becomes more negatively charged. This chemical reaction decreases the oxidation state and oxidation number of the chemical species that are undergoing reduction. An oxidizing agent undergoes reduction as it oxidizes another chemical species involved in the reaction and reduces itself.
|Parameters of Comparison||Oxidation||Reduction|
|Definition||Oxidation refers to the gain of oxygen or loss of hydrogen from a compound.||Reduction refers to the gain of hydrogen or loss of oxygen from a compound.|
|Electrons||In oxidation, a covalent compound releases electrons to the surrounding.||In reduction, a covalent compound gains electrons from the surrounding.|
|Agents||The common oxidizing agents are hydrogen peroxide and ozone.||The common reducing agents are compounds that contain metals like potassium, barium, calcium, etc and an H− ion.|
|Charge||In oxidation positive charge increase as it loses electrons.||In reduction negative charge increase as it gains electrons.|
|Oxidation Number||Oxidation leads to an increase in oxidation number.||Reduction leads to a decrease in oxidation number.|
What is Oxidation?
The definition of oxidation has changed with time, and the most recent one, in simple words, defines a process where a chemical species loses electrons and becomes more positive. Becoming more positive doesn’t necessarily mean having a positive charge. For example, if an ion X4- goes through the process of oxidation and loses two electrons, it becomes X2-. This means that it becomes more positive as (-2) oxidation state is more than (-4), but it doesn’t carry a positive charge.
If we go back to the history of chemical reactions, oxygen gas (O2) is one of the oldest known oxidizing agents. Since adding O2 in a chemical reaction led to the loss of electrons from another chemical species, oxidation was defined as a process where the presence of O2 was crucial. This definition became more predominant when iron was combined with water to form iron oxide/rust.
But, oxidation of a chemical species can or cannot contain oxygen gas necessarily. For example, when ethanol forms ethanal, it loses a hydrogen atom, which is still considered oxidation. So, the presence of particular oxygen gas is not required for oxidation. As long as a chemical species loses electrons and its oxidation state increases, oxidation takes place.
Example of oxidation reaction: 2 KI + H2O2 → I2 + 2 KOH (oxidation of iodide). Here, the oxidation number of iodide changes from (-1) to (0).
What is Reduction?
Reduction is the opposite reaction of oxidation. This is because the electrons that are lost from a chemical species are obtained by another species, which goes through reduction. During reduction, one or more than one electron is gained by an atom or a molecule, and it becomes more negatively charged. When a species goes through reduction, that compound’s oxidation state decreases.
Again, we might have confusion that a chemical compound or an ion will have a negative charge after reduction. For example, if an ion X4+ goes through the process of reduction and gains two electrons, it becomes X2+. This means that it becomes more negative as (+2) oxidation state is less than (+4), but it doesn’t carry a negative charge. So, the process of reduction doesn’t necessarily mean a negative charge. Reduction signifies the gain of electrons, and a reducing agent is responsible for an electron transfer to a species.
Consider an example, ZnO + C → Zn + CO (reduction of zinc oxide). Here, the oxidation number of zinc changes from (+2) to (0). This means it has gained to electron and has been reduced.
Main Differences Between Oxidation and Reduction
- Oxidation refers to the gain of oxygen or loss of hydrogen from a compound, whereas reduction refers to the gain of hydrogen or loss of oxygen from a compound.
- In oxidation, a covalent compound releases electrons to the surroundings, whereas, in reduction, a covalent compound gains electrons from the surrounding.
- The common oxidizing agents are hydrogen peroxide and ozone, whereas the common reducing agents are compounds that contain metals like potassium, barium, calcium, etc. and an H− ion.
- In oxidation, positive charge increase as it loses electrons, whereas, in reduction, the negative charge increases as it gains electrons.
- Oxidation leads to an increase in oxidation number, whereas reduction leads to a decrease in oxidation number.
I’ve put so much effort writing this blog post to provide value to you. It’ll be very helpful for me, if you consider sharing it on social media or with your friends/family. SHARING IS ♥️
Piyush Yadav has spent the past 25 years working as a physicist in the local community. He is a physicist passionate about making science more accessible to our readers. He holds a BSc in Natural Sciences and Post Graduate Diploma in Environmental Science. You can read more about him on his bio page.