1. The problem statement, all variables and given/known data Which of the following atoms has the largest first ionization energy? Potassium, Zinc, Gallium, or Krypton? 2. Relevant equations No equation 3. The attempt at a solution Krypton has the largest first ionization energy, but I was wondering how this question would be different if it were asking for the largest electronegativity or electron affinity? In that case, since Krypton is an ideal gas, I would think that Gallium would have the largest electronegativity and electron affinity. And if a question were asking for the largest atomic radius, the answer would be Potassium. So my question is just making sure that the only periodic trend that also pertains to ideal gases would be the ionization energy trend (increasing from left to right across the period table), and atomic radius (if a question were to ask about the largest atomic radius, it increases down a group and decreases from left to right across the periodic table). Do I have that right? Because since the ideal gases have the full octet, I would think they would not have high electronegativities. Thanks!