Concept explainers
Interpretation:
The ionic solids among
Concept Introduction:
Lattice energy is used to determine the bond strength in ionic compounds. It is the heat of formation for ions of opposite charge in the gaseous phase combine to form an ionic solid.
Lattice energy is the energy required to separate a mole of an ionic solid into gaseous ions. It cannot be measured empirically but it can be estimated by the Born-Haber cycle.
The two main factors responsible for the magnitude of the lattice energy are the charge and radius of the bonded ions. The effect of those factors is as follows:
1. If the charge of the ions increases, the lattice energy increases.
2. If the size of the ions increases, the lattice energy decreases.
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Chemistry: Principles and Practice
- What main factors control the magnitude of lattice energies? Give a specific example of a compound that should have a high lattice energy, and explain why its lattice energy is high.arrow_forwardWrite the Lewis structure for nitrosyl fluoride, FNO. Using only a periodic table, identify (a) which is the longer bond. (b) which is the stronger bond. (c) which is the more polar bond.arrow_forwardBond Enthalpy When atoms of the hypothetical element X are placed together, they rapidly undergo reaction to form the X2 molecule: X(g)+X(g)X2(g) a Would you predict that this reaction is exothermic or endothermic? Explain. b Is the bond enthalpy of X2 a positive or a negative quantity? Why? c Suppose H for the reaction is 500 kJ/mol. Estimate the bond enthalpy of the X2 molecule. d Another hypothetical molecular compound, Y2(g), has a bond enthalpy of 750 kJ/mol, and the molecular compound XY(g) has a bond enthalpy of 1500 kJ/mol. Using bond enthalpy information, calculate H for the following reaction. X2(g)+Y2(g)2XY(g) e Given the following information, as well as the information previously presented, predict whether or not the hypothetical ionic compound AX is likely to form. In this compound, A forms the A+ cation, and X forms the X anion. Be sure to justify your answer. Reaction: A(g)+12X2(g)AX(s)The first ionization energy of A(g) is 400 kJ/mol. The electron affinity of X(g) is 525 kJ/mol. The lattice energy of AX(s) is 100 kJ/mol. f If you predicted that no ionic compound would form from the reaction in Part e, what minimum amount of AX(s) lattice energy might lead to compound formation?arrow_forward
- 7.74 In a lattice, a positive ion is often surrounded by eight negative ions. We might reason, therefore, that the lattice energy should be related to eight times the potential of interaction between these oppositely charged particles. Why is this reasoning too simpler?arrow_forwardIn general the higher the charge on the ions in an ionic compound, the more favorable the lattice energy. Why do some stable ionic compounds have +1 charged ions even though +4, + 5, and +6 charged ions would have a more favorable lattice energy?arrow_forwardArrange the following series of compounds in order of increasing lattice energies. (a) NaBr, NaCl, KBr (b) MgO, CaO, CaCl2 (c) LiF, BeF2, BeOarrow_forward
- Write all resonance structures of chlorobenzene, C6H5Cl, a molecule with the same cyclic structure as benzene. In all structures, keep the CCl bond as a single bond. Which resonance structures are the most important?arrow_forwardCompare your answers from parts a and b of Exercise 69 of Chapter 3 with H values calculated for each reaction using standard enthalpies of formation in Appendix 4. Do enthalpy changes calculated from bond energies give a reasonable estimate of the actual values?arrow_forwardThink of forming an ionic compound as three steps (this is a simplification, as with all models): (I) removing an electron from the metal; (2) adding an electron to the nonmetal; and (3) allowing the metal cation and nonmetal anion to come together. a. What is the sign of the energy change for each of these three processes? b. In general, what is the sign of the sum of the first two processes? Use examples to support your answer. c. What must be the sign of the sum of the three process d. Given your answer to part c, why do ionic bonds occur? e. Given your above explanations, why is NaCl stable but not Na2Cl? NaCl2? What about MgO compared to MgO2? Mg2O?arrow_forward
- Compare your answers from parts a and b of Exercise 69 with H values calculated for each reaction using standard enthalpies of formation in Appendix 4. Do enthalpy changes calculated from bond energies give a reasonable estimate of the actual values?arrow_forwardDefine the term lattice energy. Why, energetically, do ionic compounds form? Fig. 3-8 illustrates the energy changes involved in the formation of MgO(s) and NaF(s). Why is the lattice energy of MgO(s) so different from that of NaF(s)? The magnesium oxide is composed of Mg2+ and O2 ions. Energetically, why does Mg2+O2 form and not Mg+O? Why doesnt Mg3+O3 form?arrow_forwardDistinguish between the terms electronegativity versus electron affinity, covalent bond versus ionic bond, and pure covalent bond versus polar covalent bond. Characterize the types of bonds in terms of electronegativity difference. Energetically, why do ionic and covalcnt bonds form?arrow_forward
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