Question

What is the distance in pm between the ions KBr when the first ionization energy is 0.696 aJ and the second is 0.540 aN?

Answer 1

First, you need to take into account, that the ionization is a process resulting from the atractive and repulsive electric forces between the cation (K⁺) and the anion (Br^-) in a ionic compound. Taking into account Coulomb's Law, the ionization energy is directly proportional to the ion charges (Q_cation and Q_anion) and inversely proportional to the distance between ions, as follows:


Where E is the ionization energy (E=0.696 aJ=6.96x10^-19 J), Q_cation=Q_k⁺=+1, Q_cation=Q_Br^-=-1, k is a proportionality constant (k=2.31 × 10⁻²⁸ J·m) and d the distance between the ions. Therefore, you can calculate the distance between the ions as follows:



The distance between the cation (K⁺) and the anion (Br^-) is about 331 pm.