From the following list of elements—Mg, Li, Tl, Pb, Se, Cl, Xe, Si, C—pick the one that best fits each description. Use each element only once: (a) an alkali metal, (b) an alkaline earth metal, (c) a noble gas, (d) a halogen, (e) a metalloidin group 14, (f) a nonmetal listed in group 14, (g) a metal that forms a 3+ ion, (h) a nonmetal that forms a 2- ion, (i) an element that is used as radiation shielding.