Arrange these compounds in order of increasing magnitude of lattice energy: KCl, SrO, RbBr, CaO.

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Understand that lattice energy is the energy released when gaseous ions combine to form an ionic solid. It is influenced by the charges of the ions and the distance between them, which is related to the size of the ions.

Identify the charges on the cations and anions in each compound: KCl (K+ and Cl-), SrO (Sr2+ and O2-), RbBr (Rb+ and Br-), CaO (Ca2+ and O2-).

Recognize that compounds with ions having higher charges typically have higher lattice energies because the electrostatic force between ions of higher charges is greater.

Consider the ionic radii of the cations and anions. Smaller ions lead to shorter distances between the ions in the lattice, which increases the lattice energy.

Arrange the compounds in order of increasing lattice energy based on the magnitude of ionic charges and the ionic radii. Compounds with divalent ions (Sr2+, Ca2+, and O2-) generally have higher lattice energies than those with monovalent ions (K+, Rb+, Cl-, Br-).

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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. Higher lattice energy indicates stronger ionic bonds, which typically results from smaller ions with higher charges. Understanding lattice energy is crucial for predicting the stability and solubility of ionic compounds.

Ionic Charge

The charge of the ions in an ionic compound significantly influences lattice energy. Compounds with ions that have higher charges will generally exhibit greater lattice energies due to the stronger electrostatic forces between the oppositely charged ions. For example, SrO (with Sr²⁺ and O²⁻) has a higher lattice energy than KCl (with K⁺ and Cl⁻) because of the higher charges on the ions in SrO.

Ionic Size

The size of the ions in an ionic compound affects the distance between them, which in turn influences lattice energy. Smaller ions can pack more closely together, resulting in stronger attractions and higher lattice energy. For instance, CaO has smaller ions compared to RbBr, leading to a higher lattice energy for CaO despite both being ionic compounds.