Question

question 10 of 25
which of these elements has the smallest first ionization energy?

a. na

b. li

c. rb

d. k

Explanation:

First ionization energy generally decreases down a group in the periodic table as atomic size increases (outer electrons are farther from the nucleus, easier to remove). Na, Li, Rb, K are all in Group 1. The order from top to bottom is Li, Na, K, Rb. Rb is the lowest in the group, so it has the largest atomic size and the smallest first ionization energy among them.

Answer:

C. Rb