(a) Explain the following trend in lattice energy: BeH2, 3205kJ/mol; MgH2, 2791kJ/mol ; CaH2, 2410 kJ/mol ;SrH2,...

Question:

(a) Explain the following trend in lattice energy: BeH2, 3205kJ/mol; MgH2, 2791kJ/mol ; CaH2, 2410 kJ/mol ;SrH2, 2250kJ/mol; BaH2, 2121kJ/mol.
(b) The lattice energy of ZnH2 is 2870kJ/mol. Based on the data given in part (a), the radius of the ion Zn2+ is expected to be closest to that of which group 2A element?