1. The energy required to separate the ions in a CsF crystal lattice into individual Cs* (g) and F (g) ions is known as the lattice energy of CSF (s). As shown in the table below, the lattice energy of CsF is smaller than the lattice energy of a similar compound, KF (s). Compound Lattice Energy (KJ/mol) CSF 759 KF 829 Which of the following best explains why the lattice energy of CsF is smaller than the lattice energy of KF? A. Cs has a larger ionic radius than K', so the distance between cation and anion is greater in CsF than in KF B. Cesium and fluorine have a greater electronegativity difference than potassium and fluorine, so the Cs - F bond is more polar than the K-F bond. 56 19 C. Cs+ contains more core electrons than K+, so the valence electrons in Cs are more shielded from the nucleus than the valence electrons in K'. D. Cesium has a smaller first ionization energy than potassium, so less energy is required to form the Cs than to form the Kion.