Predict the atomic number of the (as yet undiscovered) alkali -metal element in the eighth period

(a) Predict the atomic number of the (as yet undiscovered) alkali -metal element in the eighth period.
(b) Suppose the eighth-period alkali-metal atom turned out to have atomic number 137. What explanation would you give for such a high atomic number (recall that the atomic number of francium is only 87)?