Which of the following elements would you expect to have the highest ionization energy value, and why?

A. Chlorine (Cl), because it has a low effective nuclear charge and low radius

B. Fluorine (F), because it has a large radius and naturally forms a negative ion

C. Lithium (Li), because it has a small radius and naturally forms a positive ion

D. Neon (Ne), because it has a high effective nuclear charge and small radius

D. Neon (Ne), because it has a high effective nuclear charge and small radius

Explanation:

Ionization energy is the amount of energy required to remove an electron from the valence orbital.

Chlorine (Cl) and fluorine (F) are halogens which have a general valence configuration of ns²np⁵ and are highly electronegative

Lithium (Li) is an alkali metal with a valence configuration of ns¹ and has a tendency to lose electrons readily

Neon (Ne) is a noble gas with a valence configuration of ns²np⁶. Here the outer shells have a complete octet and stable configuration which makes it difficult to remove electrons. In addition the high nuclear charge and small radius of Ne results in a strong force of attraction between the nucleus and the valence electrons. Therefore, Ne would have the highest ionization energy value.

Neon, Ne, would have the highest ionization energy because it has a high effective nuclear charge and small radius.