Question

from which atom is it easiest to remove an electron? (lowest ionization energy)
f
li
be
n

Explanation:

Step1: Recall ionization energy trend

Ionization energy increases across a period and decreases down a group in the periodic table.

Step2: Analyze the elements

F (Fluorine) is in Group 17, Period 2; U (Uranium) is a large - sized actinide; Be (Beryllium) is in Group 2, Period 2; N (Nitrogen) is in Group 15, Period 2. Among these, U is a large metal - like element and has the lowest effective nuclear charge on its outermost electrons compared to the others.

Answer:

U