Consider two ionic compounds A and B. A has a larger lattice energy than B. Which of the two compounds is more stable?

When studying chemistry, one particular type of chemical species often encountered are ionic compounds. These are formed when atoms of different elements transfer electrons between them, leading to the creation of positively charged ions (cations) and negatively charged ions (anions). This electron transfer typically occurs between metals and non-metals. Metals tend to lose electrons and form cations, while non-metals tend to gain electrons to form anions.

The resulting electrostatic attraction between these oppositely charged ions creates a bond known as an ionic bond. This bonding leads to the formation of a structured array of ions known as an ionic lattice, which endows the ionic compound with a range of specific properties including high melting and boiling points, and the ability to conduct electricity when melted or dissolved in water. Due to these properties, ionic compounds are useful in various applications, ranging from household salts like sodium chloride to the magnesium used in firework sparkles.

The term chemical stability refers to the propensity of a substance to maintain its chemical composition and not react or change over time under specified conditions. It is a vital concept in chemistry as it dictates how a substance will behave when subjected to environmental factors such as temperature, pressure, or the presence of other chemicals.

A chemically stable compound resists decomposing or reacting, which is a desirable attribute for materials used in construction, pharmaceuticals, and food additives, where longevity and predictability are crucial. Factors that contribute to chemical stability include the strength of the bonds within a molecule and the energy required to break them. Ionic compounds are typically considered stable because the ionic bonds are relatively strong due to the high lattice energy, effectively resisting spontaneous breakdown.

In the context of ionic compounds, an ionic lattice is a highly ordered three-dimensional structure consisting of alternating positive and negative ions arranged in a repeating pattern. This lattice formation is the physical manifestation of the ionic bonds that occur as a result of the electrostatic forces of attraction between the ions.

The stability and physical characteristics of an ionic compound are heavily influenced by the lattice energy of the ionic lattice. The lattice energy must be overcome to break the lattice apart and melt the compound or dissolve it in a solvent. A higher lattice energy indicates a more robust lattice, which in turn imparts greater melting points, boiling points, and overall stability to the compound. Understanding the concept of lattice energy is critical for analyzing not only the stability but also the solubility and hardness of various ionic compounds.