Electronegativity vs Electron Affinity: Difference and Comparison

Electrons are subatomic particles that are present everywhere. As they have no components or substructure, they are considered elementary particles.

The electrons are essential in several physical, chemical, and electrical phenomena. They are the primary reasons why chemical reactions take place.

Two such chemical properties which require the involvement of electrons for showcasing the behaviour are Electronegativity and Electron Affinity. Both these properties are associated with electron gain and are correlated.

Electron affinity is a property that an atom in a molecule exhibits, but electronegativity is the property of an atom that has formed bonds with other atoms. The presence of electrons is essential to these chemical properties that various elements exhibit.

Key Takeaways

1. Electronegativity measures an atom’s ability to attract electrons in a covalent bond, while electron affinity is the energy released when an atom gains an electron.
2. Electronegativity is a relative property measured on a scale, while electron affinity is an absolute property measured in electronvolts.
3. Electronegativity and electron affinity are related, as atoms with higher electronegativity values also tend to have higher electron affinity values.

Electronegativity vs Electron Affinity

Electronegativity is measuring an atom’s ability to attract electrons towards itself in a chemical bond. Electron affinity is a measure of the amount of energy released or absorbed, a measure of the tendency of an atom to attract an additional electron to form a negatively charged ion.

Comparison Table

Parameter of Comparison	Electronegativity	Electro Affinity
Definition	The property of an atom attracts electrons towards it.	The property refers to energy discharge when an electron is added to an atom.
Standard Unit	It is measured in Pauling.	While it is measured in KJ per mole.
Nature	This property is qualitative.	Whereas this property is quantitative.
Associating Atom	The atom associated with it is bonded.	Here, the atom associated is attached to a molecule or is neutral.
Highest Value	The highest value is obtained when the attracting energy is high.	While in this case, the highest value is obtained when the nuclear charge is more.
Factors	The atomic number and distance between the valence electrons and the charged nucleus are the factors that affect electronegativity.	Atomic size, Nuclear charge and Electronic Configuration of the atoms are the factors that affect electron affinity.
Elements	Fluorine is the most electronegative element, while Francium is the least electronegative.	Chlorine has the highest electron affinity, while Neon has the lowest.

What is Electronegativity?

In 1811, Jöns Jacob Berzelius first introduced the term “electronegativity”. But after many more discoveries and discussions, it was only in 1932 that the property of electronegativity was fully discovered by Linus Pauling when he created an electronegative scale depending on bond enthalpies. This further aided the discovery of the Valence Bond Theory.

The chemical property of an atom to attract a shared pair of electrons towards it is called electronegativity. In simple words, electronegativity is the ability of an atom to gain electrons.

The more the atomic number, the more the distance between the nucleus and the valence electrons and the more the electronegativity. So, the atomic number and location of electrons from the nucleus are the main factors affecting electronegativity.

When two atoms having electronegativity are taken, an increasing difference between the electronegativity of the atoms will result in an increasing polar bond between them, with the atom with higher electronegativity at the negative end.

On a relative scale, electronegativity increases along a period from left to right and decreases on passing through a group. According to this, Fluorine is the most electronegative element, and Francium is the least.

What is Electron Affinity?

Electron Affinity measures the energy discharge that takes place when an electron gets added to an atom in a molecule or a neutral atom in the gaseous state, forming a negative ion. This property is donated by “Eea” and is measured in Kilo Joule (KJ) per mole.

The size of the atoms, i.e., atomic size, nuclear change and the electronic configuration of the molecule or atoms, determine the electron affinity of an atom or an element. An atom or molecule with a greater positive electron affinity value is referred to as an electron acceptor, while the one with a lower positive value is an electron donor.

The property of electron affinity is only used in the case of atoms and molecules in the gaseous state, as the energy levels of the atoms in the solid and liquid states change when they come in contact with other atoms or molecules.

Robert S. Mulliken used many electron affinities of elements to develop the electronegativity scale. Other concepts, such as chemical hardness and chemical potential, also involve the theory of electron affinity in them.

Like electronegativity, the electron affinity increases when passing through the periods and decreases down the groups. Based on this, Chlorine has the highest electron affinity value, and Neon has the lowest.

Main Differences Between Electronegativity and Electron Affinity

1. Electronegativity is the electron gain ability of atoms, while Electron affinity is the energy emitted during that.
2. Electronegativity is a qualitative property, while Electron affinity is quantitative.
3. In electronegativity, bonded atoms are involved, but in electron affinity, atoms are neutral or in a molecule.
4. One is measured in Pauling, the other in KJ/mole.
5. Atomic number and distance affect electronegativity; atomic size, nuclear charge and configuration affect electron affinity.

References

1. https://pubs.acs.org/doi/pdf/10.1021/cr50004a005