Question

Why is the highest oxidation state of a metal exhibited in its oxide or fluoride only?

Answer 1

Hint: Think about the changes which happen in a metal when it gets oxidized or reduced. Recollect the nature of oxygen and fluorine elements in the periodic table. Recollect the concepts of redox reactions and try connecting them with this problem to get the answer.

Complete step by step solution:
- Let’s take a look at the terms given in the question.
- Oxidation state represents the number of electrons either lost or gained by an element during the formation of an ion or a molecule.
- We know that metals are highly electropositive in nature and they can easily donate electrons.
- The process in which an element loses electrons is called oxidation. The elements which undergo oxidation will have positive signs due to loss of electrons which are negatively charged. They are reducing agents because they will reduce other atoms and become oxidized themselves.
- The process in which an element gains electrons is called reduction and they will have negative signs in their oxidation state. They are oxidizing agents because they will oxidize other atoms and themselves get reduced.
- Now, the highest oxidation state indicates metal that has lost the maximum number of electrons that it can lose, that is, the metal has reached its threshold limit and can’t lose any greater number of electrons. For example, Mn has the highest oxidation state +7.
- Oxygen and Fluorine are highly electronegative atoms. They are very strong oxidizing agents. That means, they easily oxidized metals and themselves get reduced by accepting electrons.
- Oxygen and Fluorine on reaction with metals form corresponding metal oxides or metal fluorides. For example, sodium, Na reacts with fluorine to form sodium fluoride, NaF. Here, sodium will have +1 oxidation state and fluorine will have -1 oxidation state.

- Therefore, the highest oxidation state of metals is exhibited by oxides and fluorides due to their high oxidizing power.


Note: Remember due to high electronegativity, oxygen and fluorine have high oxidizing power and hence, highest oxidation state of metals is achieved in their oxide or fluoride form.