Ionization Energy Definition, Types, Examples & Uses

Ionization Energy

Subject: Chemistry

Book: General Chemistry

Ionization energy is the energy required to remove an electron from a neutral atom in the gas phase. The first ionization energy removes one electron, the second removes another, and so forth. Generally, ionization energy increases across a period (due to increasing nuclear charge) and decreases down a group (due to increased distance from the nucleus). High ionization energies indicate an element is less likely to form cations.