Question

(a) Using Lewis symbols, diagram the reaction between magnesium and oxygen atoms to give the ionic substance \(\mathrm{MgO}\). (b) How many electrons are transferred? (c) Which atom loses electrons in the reaction?

Short answer

The reaction between magnesium (Mg) and oxygen (O) can be represented using Lewis symbols as follows: Mg•• + O•••••• → Mg\(\mathrm{^{2+}}\) + O\(\mathrm{^{2-}}\) → MgO. In this reaction, (b) 2 electrons are transferred and (c) the magnesium atom (Mg) loses the 2 electrons.

Step-by-step solution

Write the Lewis symbols for magnesium and oxygen

First, we need to write the Lewis symbols for magnesium (Mg) and oxygen (O) atoms. Remember that Lewis symbols represent the valence electrons of an element as dots surrounding the chemical symbol. Magnesium has 2 valence electrons and oxygen has 6 valence electrons. The Lewis symbols for Mg and O are: Mg: •• O: ••••••

Determine valence electrons

Now, let's determine the valence electrons for magnesium and oxygen. Magnesium (Mg) belongs to Group 2 of the periodic table, so it has 2 valence electrons. Oxygen (O) belongs to Group 16 of the periodic table, so it has 6 valence electrons.

Show the transfer of electrons using Lewis symbols

In the formation of an ionic compound, metals lose electrons to form cations, while non-metals gain electrons to form anions. As a metal, magnesium will lose its 2 valence electrons, while oxygen will gain those 2 electrons to complete its octet. The transfer of electrons can be represented using Lewis symbols: Mg•• + O•••••• → Mg\(\mathrm{^{2+}}\) + O\(\mathrm{^{2-}}\) → MgO In this reaction, Mg loses its 2 valence electrons to form Mg\(\mathrm{^{2+}}\) and O gains those 2 electrons to form O\(\mathrm{^{2-}}\). Thus, magnesium oxide (MgO) is formed, which is an ionic compound.

Identify the number of electrons transferred and the atom that loses electrons

(b) In this reaction, 2 electrons are transferred from Mg to O to form the ionic compound MgO. (c) The magnesium atom (Mg) loses the 2 electrons in the reaction.

Key concepts

Ionic Bonds

An ionic bond is a type of chemical bond that involves the electrostatic attraction between oppositely charged ions in a chemical compound. It's the force that holds ions together in an ionic substance like magnesium oxide (MgO). Ionic bonds typically form between metals and non-metals. Here's why that's important:

1. **Formation Process**: During the formation of an ionic bond, a metal loses electrons while a non-metal gains those electrons. This electron transfer results in positively charged ions (cations) and negatively charged ions (anions). They stick together because opposite charges attract each other.
2. **Example in MgO**: In the case of MgO, magnesium (Mg) is a metal that loses two electrons to form a Mg²⁺ ion. Oxygen (O), on the other hand, is a non-metal that gains two electrons to form an O²⁻ ion.
3. **Properties**: Ionic compounds, like MgO, are usually solid at room temperature and have high melting and boiling points because of the strong forces between the ions.

Ionic bonds are fundamental to the structure and stability of compounds, providing unique characteristics like electrical conductivity when molten or dissolved in water.

Valence Electrons

Valence electrons are the outermost electrons in an atom and are critical in determining how atoms interact. These electrons are involved in forming chemical bonds like ionic, covalent, and metallic bonds.

1. **Understanding Valence Electrons**: Each element has a set number of valence electrons based on its group in the periodic table. For example, magnesium (Mg) is in Group 2, hence it has 2 valence electrons. Oxygen (O) is in Group 16, having 6 valence electrons.
2. **Role in Bond Formation**: During chemical reactions, especially in forming ionic bonds, valence electrons are transferred between atoms to achieve a more stable electron configuration. Usually, atoms aim to satisfy the 'octet rule' which is having eight electrons in their outer shell.
3. **Lewis Symbols**: Lewis symbols, or electron dot diagrams, represent valence electrons as dots around the chemical symbol. For example, magnesium is shown as 'Mg••' and oxygen as 'O••••••'. These symbols help visualize how atoms share or transfer electrons."

Valence electrons are vital for understanding how elements chemically interact and bind together. Understanding them can help predict the types of reactions that different elements might undergo.

Electron Transfer

The concept of electron transfer is pivotal in forming ionic bonds. It involves the movement of electrons from one atom to another to achieve a stable electron configuration.

1. **Process**: In ionic bonding, electron transfer takes place from a metal to a non-metal. Metals, which have fewer valence electrons, tend to lose them, while non-metals, with more valence electrons, gain them.
2. **Example of MgO**: When magnesium forms an ionic bond with oxygen, it transfers its 2 valence electrons to oxygen. This leads to the formation of a Mg²⁺ ion for magnesium and an O²⁻ ion for oxygen.
3. **Significance**: Achieving a full outer shell adds stability. For magnesium and oxygen, this electron transfer allows both elements to achieve electron arrangements similar to noble gases, which are inherently stable.

Understanding electron transfer is key to grasping how elements bond to form compounds and how ionic substances like MgO form their specific characteristics.