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Ch.8 - Basic Concepts of Chemical Bonding
Brown - Chemistry: The Central Science 14th Edition
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232Not the one you use?Change textbook
All textbooksBrown 14th EditionCh.8 - Basic Concepts of Chemical BondingProblem 23c
Chapter 8, Problem 23c

The substances NaF and CaO are isoelectronic (have the same number of valence electrons). (c) Without looking up lattice energies, which compound is predicted to have the larger lattice energy?

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1
Identify the ions present in each compound: NaF consists of Na⁺ and F⁻ ions, while CaO consists of Ca²⁺ and O²⁻ ions.
Understand that lattice energy is influenced by the charge of the ions and the distance between them. Higher charges and smaller distances result in larger lattice energies.
Compare the charges of the ions: Na⁺ and F⁻ both have charges of ±1, while Ca²⁺ and O²⁻ have charges of ±2.
Recognize that the greater the charge on the ions, the stronger the electrostatic attraction between them, leading to a larger lattice energy.
Conclude that CaO, with its ions having higher charges (Ca²⁺ and O²⁻), is predicted to have a larger lattice energy compared to NaF, which has ions with lower charges (Na⁺ and F⁻).

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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 and higher charges. Understanding lattice energy is crucial for predicting the stability and properties of ionic compounds.
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Ionic Size and Charge

The size of the ions and their charges significantly influence lattice energy. Smaller ions can pack more closely together, leading to stronger electrostatic attractions and higher lattice energy. Additionally, ions with higher charges create stronger interactions due to the increased electrostatic force. In comparing NaF and CaO, the ionic sizes and charges of sodium, fluoride, calcium, and oxide must be considered.
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Isoelectronic Species

Isoelectronic species are atoms, ions, or molecules that have the same number of electrons. While they may have similar electronic configurations, their chemical properties can differ significantly due to differences in ionic size and charge. In the case of NaF and CaO, although they are isoelectronic, the differing charges and sizes of the ions will affect their lattice energies, making it essential to analyze these factors when predicting which compound has a larger lattice energy.
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Related Practice
Textbook Question

NaCl and KF have the same crystal structure. The only difference between the two is the distance that separates cations and anions. (a) The lattice energies of NaCl and KF are given in Table 8.1. Based on the lattice energies, would you expect the Na─Cl or the K─F distance to be longer?

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Textbook Question

(a) Does the lattice energy of an ionic solid increase or decrease (i) as the charges of the ions increase, (ii) as the sizes of the ions increase?

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Textbook Question

NaCl and KF have the same crystal structure. The only difference between the two is the distance that separates cations and anions. (b) Use the ionic radii given in Figure 7.8 to estimate the Na─Cl and K─F distances.

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Textbook Question

(b) Arrange the following substances not listed in Table 8.1 according to their expected lattice energies, listing them from lowest lattice energy to the highest: MgS, KI, GaN, LiBr.

Textbook Question

The substances NaF and CaO are isoelectronic (have the same number of valence electrons). (b) What are the charges of each of the anions in each compound?

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Textbook Question

Consider the ionic compounds KF, NaCl, NaBr, and LiCl. (a) Use ionic radii (Figure 7.8) to estimate the cation–anion distance for each compound.

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