Cs atoms when excited to their 7 P-2, 8 P-2, and 9 P-2 states have sufficient internal energy to be able to react with H-2 molecules forming CsH and H and they do so. Cs 9 P-2 has sufficient energy to react with alkanes; in fact, this does not occur. Instead an efficient n changing but l conserving collision occurs producing Cs atoms in the lower P-2 states. This phenomenon is shown to result from the fact that in the Rydberg state the valence electron is remote from the Cs+ ion core. Cs 9 P-2 does react with propene removing an allylic H atom to form CsH.