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Ch.8 - Basic Concepts of Chemical Bonding
Chapter 8, Problem 21a

(a) Is lattice energy usually endothermic or exothermic?

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1
Understand the concept of lattice energy: Lattice energy is the energy required to form a crystalline lattice from gaseous ions. It is a measure of the strength of the forces between the ions in an ionic solid.
Recognize the nature of lattice energy: Lattice energy is typically exothermic, meaning it releases energy when the ionic lattice is formed from gaseous ions.
Consider the process of forming an ionic solid: When ions come together to form a solid, they release energy due to the electrostatic attraction between oppositely charged ions.
Relate lattice energy to stability: The release of energy during the formation of the lattice contributes to the stability of the ionic compound. A higher lattice energy indicates a more stable ionic solid.
Connect lattice energy to other thermodynamic processes: While lattice energy is exothermic, the overall formation of an ionic compound from its elements involves both endothermic and exothermic steps, such as ionization energy and electron affinity.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Lattice Energy

Lattice energy is the energy released when gaseous ions combine to form an ionic solid. It is a measure of the strength of the forces between the ions in an ionic compound. A higher lattice energy indicates a more stable ionic compound due to stronger ionic bonds.
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Exothermic vs. Endothermic Processes

Exothermic processes release energy, usually in the form of heat, to the surroundings, resulting in a temperature increase. In contrast, endothermic processes absorb energy from the surroundings, leading to a temperature decrease. The sign of the energy change is crucial in determining whether a process is exothermic or endothermic.
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Formation of Ionic Compounds

The formation of ionic compounds involves the transfer of electrons from metals to nonmetals, resulting in the creation of positively and negatively charged ions. The attraction between these oppositely charged ions is what forms the ionic bond, and the energy associated with this process is reflected in the lattice energy, which is typically exothermic.
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