Question

6/17 choose the element with the highest ionization energy.

Explanation:

Step1: Recall ionization - energy trend

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

Step2: Identify the position

Noble - gases have the highest ionization energies in their respective periods due to their stable electron configurations. Among all noble - gases, helium has the highest first - ionization energy because it has a small atomic radius and a stable 1s² electron configuration.

Answer:

Helium