Understanding the Concept

* Valency: The combining power of an element, specifically the number of electrons an atom can gain, lose, or share when forming chemical bonds.

* Oxidation State: A number assigned to an atom in a molecule that represents the number of electrons it has gained or lost relative to its neutral state.

Analyzing Fe₃O₄ (Magnetite)

1. Oxygen's Valency: Oxygen typically has a valency of -2 (it gains two electrons to achieve a stable octet).

2. Charge Balance: In a neutral compound, the total positive charges must equal the total negative charges.

* There are 4 oxygen atoms (4 x -2 = -8) in Fe₃O₄.

* Therefore, the total positive charge from the iron atoms must be +8.

3. Iron's Valency: We have three iron atoms, so to achieve a total +8 charge, there needs to be a mix of valencies. The most common valencies for iron are +2 and +3.

4. Determining the Valencies: The only way to get a total of +8 with three iron atoms is to have two iron atoms with a +3 valency (+3 x 2 = +6) and one iron atom with a +2 valency.

Conclusion

In Fe₃O₄, two iron atoms have a valency of +3, and one iron atom has a valency of +2. This is often represented as Fe²⁺Fe₂³⁺O₄.