Question

Oxidation was once defined as chemically adding oxygen to a substance. Use this reaction to argue that this definition is consistent with the modern definition of oxidation. $$ 2 \mathrm{Mg}+\mathrm{O}_{2} \rightarrow 2 \mathrm{MgO} $$

Short answer

Adding oxygen involves electron loss, consistent with modern oxidation definition.

Step-by-step solution

Understanding Traditional Definition of Oxidation

Traditionally, oxidation was defined as the chemical process of adding oxygen to a substance. In the reaction \(2\, \text{Mg} + \text{O}_2 \rightarrow 2\, \text{MgO}\), magnesium (Mg) is combined with oxygen (\(\text{O}_2\)) to form magnesium oxide (\(\text{MgO}\)). The product \(\text{MgO}\) contains oxygen that was not present in the reactant \(\text{Mg}\). This shows the addition of oxygen.

Understanding Modern Definition of Oxidation

In modern chemistry, oxidation is defined broadly as the loss of electrons by an atom, molecule, or ion. When magnesium (\(\text{Mg}\)) reacts with oxygen (\(\text{O}_2\)), each magnesium atom loses two electrons to form \(\text{Mg}^{2+}\) ions. This electron loss by magnesium fits the modern definition of oxidation.

Comparing Traditional and Modern Definitions

Both definitions align because, in the reaction \(2\, \text{Mg} + \text{O}_2 \rightarrow 2\, \text{MgO}\), magnesium atoms not only gain oxygen (traditional definition) but also lose electrons to form \(\text{Mg}^{2+}\) ions (modern definition). Therefore, both the addition of oxygen and the loss of electrons occur, showing that traditional oxidation as adding oxygen is consistent with the modern understanding of electron transfer.

Key concepts

Chemical reactions

Chemical reactions are processes where substances, known as reactants, are transformed into different substances called products. These transformations involve making and breaking chemical bonds, rearranging the atoms to form new products. In a reaction like \(2 \, \text{Mg} + \text{O}_2 \rightarrow 2 \, \text{MgO}\), magnesium (Mg) and oxygen (O\(_2\)) are the reactants, while magnesium oxide (MgO) is the product. Chemical reactions can be categorized in many ways, one of which is by looking at the specific changes happening at the molecular level:

• Synthesis reactions: These involve combining simple substances to form a more complex product, such as in the formation of magnesium oxide.
• Redox reactions: Redox stands for reduction-oxidation reactions. They involve the transfer of electrons between two species.

Understanding these categories helps in identifying the transformation that reactants undergo during the reaction.

Electron transfer

Electron transfer is at the heart of many chemical reactions, especially redox reactions. It involves the movement of electrons from one atom to another, changing the charge of the atoms involved. In the modern definition of oxidation, this involves an atom or molecule losing electrons.In the reaction \(2 \, \text{Mg} + \text{O}_2 \rightarrow 2 \, \text{MgO}\), each magnesium atom loses two electrons. These electrons are gained by the oxygen molecules. Let's break this down:

• Oxidation process: Magnesium atoms lose electrons to form Mg\(^{2+}\) ions, as it donates two electrons.
• Reduction process: Oxygen molecules gain these electrons, which helps form the oxide ions in MgO.

This electron transfer is key to the modern understanding of oxidation, showing how traditional concepts like adding oxygen relate to electron loss.

Magnesium oxide formation

The formation of magnesium oxide (MgO) from magnesium and oxygen is a classic example of an oxidation reaction. This reaction shows how both traditional and modern definitions of oxidation can coexist. Here's why:

• Under traditional terms, magnesium combines with oxygen. This results in magnesium oxygenated to form MgO.
• In modern terms, as the Mg atoms lose electrons to form Mg\(^{2+}\), these electrons are then accepted by O\(_2\), leading to the formation of oxide ions, O\(^{2-}\).

Both these perspectives show the transformation that occurs in the magnesium oxide formation, highlighting how oxidation is a dual process of oxygen addition and electron transfer. Magnesium oxide is a stable compound, demonstrating the importance of bond formation and energy considerations in chemical reactions.