What is the oxidation number of Mg in Mg²⁺?

The oxidation number of magnesium (Mg) in the ion Mg²⁺ is +2. This is because the oxidation number reflects the charge of the ion. When magnesium loses two electrons, it becomes positively charged, resulting in the +2 oxidation state.

Understanding Oxidation Numbers

To grasp why Mg has an oxidation number of +2, it's essential to understand what oxidation numbers represent. Oxidation numbers indicate the degree of oxidation of an atom in a compound or ion. They help in tracking how many electrons an atom has gained or lost during chemical reactions.

Determining the Oxidation State

In the case of magnesium, it is located in Group 2 of the periodic table, which is known as the alkaline earth metals. Elements in this group typically have two electrons in their outermost shell. When magnesium forms an ion, it tends to lose these two electrons to achieve a stable electron configuration, similar to that of the noble gases.

• Neutral Magnesium Atom: A neutral magnesium atom has 12 protons and 12 electrons, resulting in no overall charge.
• Formation of Mg²⁺: When it loses two electrons, it has 12 protons and only 10 electrons, leading to a net positive charge of +2.

Examples of Oxidation States

To further illustrate, let’s compare magnesium with another element, like sodium (Na). Sodium, which is in Group 1, loses one electron to form Na⁺ with an oxidation number of +1. In contrast, magnesium, by losing two electrons, forms Mg²⁺ with an oxidation number of +2. This difference is a direct result of their positions in the periodic table and their electron configurations.

Practical Implications

Understanding the oxidation state of magnesium is crucial in various chemical contexts, such as in reactions involving ionic compounds. For instance, when magnesium reacts with chlorine (Cl), it forms magnesium chloride (MgCl₂). In this compound, magnesium retains its +2 oxidation state, while each chlorine atom has an oxidation state of -1, balancing the overall charge of the compound.

In summary, the oxidation number of magnesium in the Mg²⁺ ion is +2, reflecting its tendency to lose two electrons to achieve a stable electronic configuration. This concept is fundamental in chemistry, as it helps predict how elements will interact in chemical reactions.