Electron Affinity

Atoms and Molecules - Periodic Trends


Concept Definition

Study the primary definition of this concept, broken into general, basic, and advanced English definitions. Also see the mathematical definition and any requisite background information, such as conditions or previous definitions.


The first electron affinity is the energy released when one mole of gaseous atoms each aquire an electron to form one mole of gaseous 1- ions.


The energy change that occurs as an atom or negative ion accepts an electron. The first electron affinity applies to a neutral atom combining with an electron; the second electron affinity applies to a minus-one ion accepting an electron; etc. Sometimes defined as negative when the negative ion is more stable than the neutral atom and sometimes defined as positive for the same circumstance; check the definition in any source of data.

Mathematical Definition

Atom(g) + electron- → Anion-(g) + energy(electron affinity)



Learn important vocabulary for this concept, including words that might appear in assessments (tests, quizzes, homework, etc.) that indicate the use of this concept.

 Important Vocabulary

Term Context
  • Cl- is an anion.
  • Halogens form anions with a 1- charge.
  • Fluorine, with a high electron affinity, is very good at accepting an electron and becoming the F- anion.



Browse relevant videos from the Journal of Chemical Education's (JCE) Chemistry Comes Alive! library and other video sources.

Periodic Trends: Electron Affinity

A visual representation of the changes in electron affinity as one moves down and across the periodic table.


Computer Animations

Experience computer simulators or animations that illustrate the concept discussed here. Many simulators or animations come with worksheets for use in class.
ChemEd DL http://www.chemeddl.org/resources/ptl/index.php

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