The oxidation number (or oxidation state) of an element in a compound tells us how many electrons an atom has gained, lost, or shared in a chemical reaction. It’s a way to keep track of how atoms behave in a chemical process, like a number showing how “oxidized” or “reduced” an atom is.
Here’s a simple way to understand it:
In their pure form, elements like oxygen (O), hydrogen (H), and iron (Fe) have an oxidation number of zero (0). For example, in O₂ (oxygen molecule) or Fe (iron), the oxidation number of both oxygen and iron is 0 because they haven't gained or lost any electrons.
When atoms form compounds, they usually lose or gain electrons. For example, in H₂O (water), hydrogen has an oxidation number of +1, and oxygen has an oxidation number of -2. This is because oxygen tends to attract electrons more than hydrogen.
Here are a few basic rules to remember:
Oxidation numbers are used to understand redox (reduction-oxidation) reactions, where one substance loses electrons (oxidation) and another gains them (reduction). This helps in balancing chemical equations and knowing how different substances interact.
In short, oxidation numbers are like the “scorecards” in chemical reactions, showing how atoms behave in terms of their electrons.
In terms of significance, usage, representation, and charge indication, oxidation states and oxidation numbers are not interchangeable.
The highest oxidation state that may be set to an element is +9, and it cannot go higher than that.
Oxidation state is important in determining the strength of acids and bases, as well as determining the charge of an atom in a chemical reaction. While a rise in oxidation state implies that an acid's strength is increasing, it also shows that a base's strength is decreasing.