What is the differ between constant speed and acceleration

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 large 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