What is the Difference Between Ionization Energy and Electron Affinity?

Ionization energy and electron affinity are two distinct concepts in chemistry. Here are the main differences between them:

• Ionization Energy: This is the amount of energy required to remove an electron from an atom. It is a positive value because energy is needed to remove the electron. Ionization energy generally increases across a row on the periodic table and is minimum for the alkali metals, which have a single electron outside a closed shell.
• Electron Affinity: This is the amount of energy released when an atom gains an electron. It is a negative value because energy is released during the process. Electron affinities are more difficult to measure than ionization energies and are usually known to fewer significant figures.

In summary:

• Ionization energy is the energy required to remove an electron from an atom.
• Electron affinity is the energy released when an atom gains an electron.

While there is a relationship between ionization energy and electron affinity, they are not the same energy and have different sign conventions.

Comparative Table: Ionization Energy vs Electron Affinity

Ionization energy and electron affinity are both related to an atom's ability to attract or hold electrons, but they represent different concepts and processes. Here is a comparison between the two:

Both ionization energy and electron affinity follow similar trends in the periodic table, as they are influenced by factors such as atomic size and electronegativity. However, they are not the same, and their values are typically different for a given element. For example, ionization energy is always measured in kilojoules per mole (kJ/mol), while electron affinity is typically given in kilojoules per mole (kJ/mol) but can be negative, indicating that energy is released during the process.