While writing the formula of ferrous oxide it is written as `(FeO)`, because it is

Options

A. Non-stoichiometric
B. Non-existant
C. Paramagnetic
D. Ferromagnetic

Answer

To understand why the formula for ferrous oxide is written as FeO, we need to analyze the oxidation states of iron in this compound and the concept of non-stoichiometry.

### Step-by-Step Solution:

1. **Identify the Oxidation State of Iron in Ferrous Oxide:**
- In ferrous oxide (FeO), iron (Fe) has an oxidation state of +2. This is because oxygen (O) typically has an oxidation state of -2. To balance the charges in the compound, iron must be +2.

2. **Understanding the Formula:**
- The formula FeO indicates that there is one iron atom (Fe) with a +2 charge and one oxygen atom (O) with a -2 charge. This results in a neutral compound overall.

3. **Comparison with Ferric Oxide:**
- In contrast, ferric oxide (Fe2O3) contains iron in the +3 oxidation state. Here, two iron atoms contribute a total of +6, which is balanced by three oxygen atoms contributing a total of -6.

4. **Concept of Non-Stoichiometry:**
- Non-stoichiometric compounds are those that do not have a fixed ratio of their constituent elements. In the case of ferrous oxide, it can exhibit non-stoichiometric behavior, meaning that the ratio of iron to oxygen can vary slightly under certain conditions.

5. **Conclusion:**
- Therefore, the formula FeO for ferrous oxide is derived from the +2 oxidation state of iron and the -2 oxidation state of oxygen. The correct answer to the question is that it is due to "non-stoichiometry."

### Final Answer:
The formula for ferrous oxide is written as FeO because it exhibits non-stoichiometric behavior.