The Correct Answer and Explanation is:
The question asks which of the following compounds has the highest lattice energy: Li2O or Li3N.
Answer: Li3N
Explanation:
Lattice energy refers to the energy released when ions in the gas phase come together to form a solid ionic compound. It is influenced by two main factors:
- Ion Charge: Higher charged ions lead to a greater electrostatic attraction between the ions, resulting in a higher lattice energy.
- Ion Size (Ion Radius): Smaller ions lead to stronger electrostatic forces between them, increasing lattice energy.
Let’s break down each compound:
- Li2O (Lithium Oxide): In this compound, lithium (Li) has a charge of +1, and oxygen (O) has a charge of -2. The ions involved are Li⁺ and O²⁻. Since the charge on oxygen is higher than that of nitrogen in Li3N, there is a relatively strong electrostatic attraction between Li⁺ and O²⁻. However, the size of the O²⁻ ion is relatively large, which reduces the lattice energy slightly.
- Li3N (Lithium Nitride): Here, lithium (Li) has a +1 charge, and nitrogen (N) has a -3 charge. The nitrogen ion (N³⁻) carries a higher negative charge than oxygen, resulting in a much stronger electrostatic attraction between Li⁺ and N³⁻. Additionally, the nitrogen ion is smaller than the oxide ion, which increases the lattice energy even further.
The combination of a higher charge on the nitrogen ion and its smaller size compared to oxygen gives Li3N a higher lattice energy than Li2O. Hence, Li3N has the highest lattice energy.
