Electronegativity vs Electron Affinity

Electronegativity and electron affinity are two concepts that are often encountered by students when understanding bonding of two atoms to make a molecule. Though very similar, there are differences in the two terms that need to be highlighted. Electronegativity is the property of an atom to bind with another atom while electron affinity is the power of an atom to attract the bond pair towards itself in the molecule. In general, atoms that have high electron affinity tend to be more electronegative.

Electron affinity is the amount of energy released when an atom acquires an electron. More the energy is released, more readily an atom becomes and ion. Thus it is the ability of an atom to attract additional electrons. Electron affinity or Eea of an atom of a molecule is represented by the following chemical equation.

X- → X + e−

In some cases, electron does not need to be detached from a molecule to form a bond with another. Here, electron is shared and a covalent bond is formed. Electronegativity is thus the measure of the ability of a molecule to attract an electron and form a covalent bond. Higher electronegativity thus indicates the stronger pull exerted by a molecule to pull electrons towards it.

Difference Between Electronegativity and Electron Affinity

Electronegativity is a concept that is not quantifiable and used to explain making of covalent bonds and bond polarity. On the other hand, electron affinity can be easily measured by calculating the amount of energy released when an electron is detached from an atom to become an ion. Electronegativity is a concept that tells us that the location of the bonding pair of electrons in a molecule. This pair is localized more towards the atom which is more electronegative of the two. Another difference is that while electron affinity deals with a single atom, while electron affinity deals with atoms in a molecule. The way oxygen atom attracts electrons is electronegativity, while the phenomenon of chlorine taking an electron from sodium is electron affinity. Finally, electronegativity is a property, while electron affinity is a measurement.

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