AAMC FL Practice Exam

What does ionization energy refer to?

1. The energy required to gain an electron

2. The energy required to remove an electron from an atom

3. The energy released when an electron is added

4. The energy required for bond formation

The correct answer is: The energy required to remove an electron from an atom

Ionization energy specifically refers to the amount of energy needed to remove an electron from a neutral atom or molecule. This energy is a crucial property in chemistry as it helps to determine how easily an atom can lose an electron and thus its reactivity. When an atom loses an electron, it becomes a positively charged ion. The energy required to overcome the attraction between the nucleus and the negatively charged electron reflects the strength of that attraction. As such, ionization energy typically increases across a period in the periodic table, as atoms have more protons pulling on electrons, and it generally decreases down a group due to increased distance from the nucleus and the shielding effect of inner electrons. The other options relate to different processes: gaining an electron corresponds to electron affinity, the energy released when an electron is added is also tied to the concept of electron affinity, and the energy required for bond formation involves different types of interactions, such as covalent or ionic bonding. Thus, the definition of ionization energy is distinct and focuses specifically on the removal of an electron.