Oxidation number | Oxidation state rules

Oxidation Number

Oxidation number, also called oxidation state, is the total number of electrons that benefits or loses to make an atom a chemical bond with another atom.

What are the Oxidation Numbers?

Chemists use an oxidation number (or oxidation state) to track the number of electrons of atoms in atoms. Oxidation numbers do not always match the actual charges on the molecules, and we can calculate the oxidation number for atoms involved in the covalent (as well as ionic) bond.
Let’s understand the oxidation numbers with some examples!

Guidelines for determining oxidation number

Oxidation numbers are usually written first with sign (++ or -), then the magnitude, which is in contrast to the charges on ions. Chemists use the following guidelines to determine the oxidation number:
Step 1.  In their original state the atoms have an oxidation number of 0.
Step 2.  In the monatomic (i.e. single atomic) ions, the atoms have an oxidation number equal to their charge.
Step 3.  In compounds: Fluorine oxidation number is assigned -1; Oxygen is usually assigned a -2 oxidation number (except peroxide compounds where it is -1, and in binary compounds with fluorine where it is positive); And hydrogen is usually assigned a +1 oxidation number, except that when the hydride ion is present in the form of H, then in which case rule 2 wins.
Step 4.  In compounds, the oxidation number is assigned to all other atoms so that the sum of oxidation numbers on all atoms in species is equal to the charge on the species.

Oxidation Number Usage: Oxidation and Reduction

Now we can follow the instructions to find the oxidation number. This is good, but why the oxidation state matters? After all, they are practically imaginary!

Chemists are usually interested in keeping track of electrons because we want to know that the electrons are transferred from one atom to the other. In the above example, we can see that the oxidation status of hydrogen differs in compared to H2O. If we compare oxidation states, then a chemist can say that hydrogen in water has fewer electrons compared to the original hydrogen.

We will see that this reaction not only breaks and creates new chemical bonds, but also includes the loss of electrons from H2. Chemists have specific words to describe those processes, which include the loss or benefits of electrons:
Oxidation is the loss of one or more electrons by an atom. When the oxidation number of the element increases, it means that the electrons are damaged and that element is oxidized. In the above reaction,HOxidation is being done because it loses electrons to make H2O. The loss of electrons is evident from the oxidation number changing from  to +1: Since hydrogen atom loses an electron (which has a negative charge), the oxidized number has increased.
The cut is the advantage of one or more electrons by an atom. When the oxidation number of element decreases, it means that the electrons have the benefit and that element is decreasing. In reaction to making water,O2​ Is being reduced because the oxidation number of every oxygen atom has fallen from 0 to -2 due to the benefit of 2 negatively charged electrons.

Some ways to remember oxidation and reduction include:
1.  OIL RIG: “Oxidation is Damage” and “Decrease Is Increased”
2.  LEO the lion says GER: “The loss of electron is oxidation” and “the benefits of electrons are lacking”
Oxidizing agents and decreasing agents are closely related to oxidation and reduction.
A decreasing agent, or refractor, loses electrons and therefore oxidizes in the chemical reaction. In our example, HWorking in the form of a decreasing agent in response, because it is oxidation and the cause of a reduction of O

An oxidizing agent, or oxidant, receives electrons and decreases in the chemical reaction. OWorking in the form of an oxidizing agent in our reaction as it is responsible for the oxidation of declining agents,H2

Oxidation Numbers and Redox Reactions

Chemical reactions involving electron reactions are called oxidation-reduction or redox responses. Oxidation state change is an indication that an electron transfer is happening. All redox responses include both reduction and oxidation.
Many reaction types such as combustion, single replacement, and some synthesis and decompression reactions fall into the category of Radox responses. Oxidation numbers and radox responses are also important concepts in more advanced chemistry classes, such as biochemistry, electrochemistry, biological chemistry, and inorganic chemistry. We will not give more information about Radox responses in this article, but keep in mind that it will be easy to stay comfortable with oxidation numbers!


An oxidation number is used by chemists to keep track of electrons within a compound. We can use the guidelines to allocate oxidation numbers to the atoms in the complex. During the reaction, changes in the oxidation state tell us that the electrons are transferred. Reactions involving the transfer of electrons are called radox responses, and they include reduction (the gain of electrons) and oxidation (loss of electrons). The substance that is used is called an oxidizing agent, and is called an oxidized substance reducing agent.

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