**Oxidation Number of Metal Ion M 3**

The oxidation number of a metal ion can be determined by considering the number of electrons it loses or gains during a chemical reaction. In this case, the metal ion M 3 loses 3 electrons. To understand the oxidation number of M 3, we need to explore the concept of oxidation and reduction.

**Oxidation and Reduction**

Oxidation and reduction are two fundamental processes that occur during chemical reactions. Oxidation refers to the loss of electrons, while reduction refers to the gain of electrons. These processes always occur together and are commonly referred to as redox reactions.

**Determining Oxidation Number**

The oxidation number of an atom in a molecule or ion is a measure of its electron distribution. It indicates the charge that the atom would have if the electron pairs in the bonds were completely transferred to the more electronegative element.

To determine the oxidation number of an atom in a compound, we follow certain rules:

1. **Oxidation Number of an Uncombined Element**: The oxidation number of an uncombined element is always zero. Therefore, the oxidation number of M in its elemental state would be zero.

2. **Oxidation Number of a Monatomic Ion**: The oxidation number of a monatomic ion is equal to its charge. Since M 3 loses 3 electrons, its charge would be +3.

3. **Oxidation Number of Oxygen**: In most compounds, oxygen has an oxidation number of -2. However, there are a few exceptions to this rule, such as peroxides (e.g., H2O2) where oxygen has an oxidation number of -1.

4. **Oxidation Number of Hydrogen**: In most compounds, hydrogen has an oxidation number of +1. However, there are exceptions when it is bonded to a metal, such as in metal hydrides, where its oxidation number is -1.

5. **Oxidation Number of Other Elements**: For other elements, the oxidation number can be determined by applying the rules mentioned above and considering the overall charge of the compound.

**Oxidation Number of Metal Ion M 3**

Since the metal ion M 3 loses 3 electrons, its oxidation number would be +3. This means that M has a positive charge of 3 when it forms an ion.

In summary, the metal ion M 3 has an oxidation number of +3 since it loses 3 electrons during a chemical reaction. The oxidation number is a measure of the electron distribution and indicates the charge that the atom would have if the electron pairs in the bonds were completely transferred to the more electronegative element.