Question

Which of the following is the expected product of the reaction of \(\mathrm{Mg}(s)\) and \(\mathrm{N}_{2}(g)\) under heat? (i) \(\mathrm{Mg}_{3} \mathrm{~N}(s)\) (ii) \(\mathrm{MgN}_{2}(s)\) (iii) \(\mathrm{Mg}_{3} \mathrm{~N}_{2}(s),\) (iv) \(\mathrm{Mg}(s)\) and \(\mathrm{N}_{2}(g)\) will not react with one another.

Short answer

The expected product of the reaction of Mg(s) and N₂(g) under heat is \(Mg_3N_2(s)\).

Step-by-step solution

Identify the type of reaction

Magnesium (Mg) is a metal and Nitrogen (N₂) is a non-metal. When a metal reacts with a non-metal, they usually form an ionic compound. This means we need to look for an ionic compound in the given options. Step 2: Determine the charges of the ions

Determine the charges of the ions

Magnesium (Mg) has a valency of +2, as it has two electrons in the outer shell that it can lose. Nitrogen (N) has a valency of -3, as it has five electrons in the outer shell, requiring three more electrons to complete its octet. Now, we will use these charges to figure out the correct product. Step 3: Find the correct product

Find the correct product

In an ionic compound, the charges of its ions must balance. We are given four options for possible products: (i): \(Mg_3N(s)\): Charges: (+2) + (-3) = -1, which is not balanced. (ii): \(MgN_2(s)\): Charges: (+2) + 2*(-3) = -4, which is not balanced. (iii): \(Mg_3N_2(s)\): Charges: 3*(+2) + 2*(-3) = 0, which is balanced. (iv): \(Mg(s)\) and \(N_2(g)\) do not react: This is a possibility if none of the other options are correct. The only option that gives a charge balance is option (iii), which is therefore our answer. Answer: The expected product of the reaction of Mg(s) and N₂(g) under heat is \(Mg_3N_2(s)\).

Key concepts

Ionic Compounds

Ionic compounds are a type of chemical compound that consists of ions held together by electrostatic forces known as ionic bonds. These compounds often form between a metal and a non-metal. In the solid state, ionic compounds arrange in a crystal lattice, which is a highly ordered structure. This arrangement contributes to their high melting and boiling points, as well as their typical hardness and brittleness.

When forming ionic compounds, metals, which tend to lose electrons, become positively charged ions or cations. Non-metals, which tend to gain electrons, become negatively charged ions or anions. By losing or gaining electrons, these atoms achieve a more stable electron configuration, often resembling that of the nearest noble gas. The ionic bonds create the balance that keeps the compound together.

Metal and Non-metal Reactions

When metals react with non-metals, they often engage in ionic bonding due to their differences in electron affinity. Metals, having low electronegativity, are prone to losing electrons. This gives them a positive charge. Non-metals have high electronegativity and a tendency to gain electrons, resulting in a negative charge. These opposite charges attract, pulling the two ions together to form an ionic compound.

In the specific reaction of magnesium (\(\text{Mg} \)) and nitrogen (\(\text{N}_2\)), magnesium acts as the metal that loses electrons and nitrogen as the non-metal that gains electrons. This reaction is energetically favorable under heat. The ionic compound formed from this reaction is magnesium nitride (\(\text{Mg}_3\text{N}_2\)). This process reveals the underlying principle of metal-non-metal reactions which is the transfer of electrons to form ionic bonds.

Charge Balancing

Charge balancing is a crucial concept in the formation of ionic compounds because it ensures that the resulting compound is electrically neutral. Each compound must have an equal number of positive and negative charges.

To achieve this, the charges of the metal cations and non-metal anions must be balanced. For example, in the case of magnesium and nitrogen, magnesium atoms lose two electrons each (resulting in a +2 charge), while nitrogen atoms gain three electrons each (resulting in a -3 charge). Therefore, three magnesium ions (\(3*+2\)) and two nitrogen ions (\(2*-3\)) are needed to balance the charges to zero:

• Positive charge: \(3 \times +2 = +6\)
• Negative charge: \(2 \times -3 = -6\)

The sum of +6 and -6 equals zero, hence fulfilling the charge balance and forming a stable ionic compound, \(\text{Mg}_3\text{N}_2\). Charge balancing like this is essential to determining the correct formula for ionic compounds.