Which type of ion is likely to have the greatest ionization energy?

Ionization energy refers to the amount of energy required to remove an electron from an atom or ion in its gaseous state. Generally, the trend in ionization energy increases across a period on the periodic table and decreases down a group.

Cations, which are positively charged ions that have lost one or more electrons, typically have higher ionization energies compared to neutral atoms or anions. This is because cations have a stronger effective nuclear charge acting on their remaining electrons. When electrons are removed to form a cation, the remaining electrons experience less electron-electron repulsion and are held more tightly by the positively charged nucleus.

Conversely, anions are negatively charged ions formed by gaining electrons, which generally leads to increased electron-electron repulsion within the atom. This makes it easier to remove an electron from an anion than from a cation. Therefore, anions typically have lower ionization energies.

Neutral atoms, while having their electrons more loosely bound than cations, also do not exhibit the stronger attractive forces that cations experience. Molecules may also vary widely in ionization energy depending on their composition and structure, but they are not typically compared directly within this context.

Thus, cations generally exhibit the greatest ionization