5.06 – Ionization & Lattice Energy

We are already familiar with the concept of ionization from our experience with the photoelectric effect and PES.  Now we will go deeper into each step in the ionization process, as well as the energy steps needed to form salts from their elements.

Lesson Objectives

  • Write Lewis symbols for atoms and ions. (8.1)
  • Define lattice energy and be able to arrange compounds in order of increasing lattice energy based on the charges and sizes of the ions involved. (8.2)

To become familiar with the topics presented in this mission, view the slides below and take note of the key ideas.  These are from sections 8.1 and 8.2 of your text.

Now work through the practice problems, and post your work to OneNote.

Work out the problems below, and check your work before submitting it into OneNote.


(a) Based on the lattice energies of MgCl2 (2326 kJ/mol) and SrCl2 (2127 kJ/mol), what is the range of values that you would expect for the lattice energy of CaCl2?

(b) Using data from Appendix C, Figure 7.10, Figure 7.12 and the value of the second ionization energy for Ca, 1145 kJ/mol, calculate the lattice energy of CaCl2.

8.99    The electron affinity of oxygen is -141 kJ/mol, corresponding to the reaction

O(g) + e → O(g)

The lattice energy of K2O(s) is 2238 kJ/mol.  Use these data along with data in Appendix C and Figure 7.12 to calculate the “second electron affinity” of oxygen, corresponding to the reaction

O(g) + e → O2–(g)


2005 FRQ #7


Well done!  Now it's time to explore the complexities of covalent bonding :)

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