Answer all the questions (10 points) 19. Define ionic radius. How does size change when an atom becomes a) an anion and b) a cation? 20. Based on the position in the periodic table, choose for each pair, the atom with the largest atomic radius in each of the following pairs: a) Na, Cs; b) Be, Ba; c) N, Sb; d) F, Br; e) Ne, Xe. 21. Arrange the following atoms in order of decreasing atomic radius: Na, Al, P, Cl, and Mg. 22. In each of the following pairs, indicate which species is smaller: a) Cl or Cl- , b) Na or Na+; c) O2- or S2- d) Mg2+ or Al3+; e) Au+ or Au3+. 23. Arrange the following ions in increasing order of ionic radius: N3-, Na+, F-, Mg2+, O2-. 24. Define ionization energy. Generally, ionization energies are measured for atoms in the gaseous state. Because?