A Level Chemistry OCR Practice Exam 2025 - Free Chemistry Practice Questions and Study Guide

The energy required to remove one electron from each ion in one mole of gaseous ions is referred to as first ionization energy. This process involves overcoming the attraction between the negatively charged electron and the positively charged nucleus of the ion, which requires energy input.

First ionization energy is defined as the energy needed to remove the highest energy electron from a neutral atom. When this concept is applied to ions, particularly when the ions are in a gaseous state, the energy measured reflects the ion's ability to hold onto its electrons.

The other terms, while related to the concepts of electron interactions, refer to different processes. Second ionization energy, for instance, is the energy needed to remove a second electron from an already positively charged ion, indicating that a different level of energy is required due to the increased positive charge of the ion. Electron affinity is the energy change when an electron is added to a neutral atom, which has a different conceptual focus. Electronegativity refers to the tendency of an atom to attract electrons when involved in a chemical bond; it does not relate directly to the energy required to remove electrons from ions.

Understanding first ionization energy is crucial, as it has implications for the reactivity and characteristics of elements, especially