Electron Affinity Definition Trend Properties and Examples

The periodic table is a type of scheme in which it is possible to find the representation of all the chemicalElectron Affinity elements that exist depending on their atomic number, in it, it is possible to find period groups of elements in which the elements that share some characteristics are located physical and chemical. One of these characteristics is known by the name of electron affinity.

What is Electron Affinity?

The electron affinity is one of the periodic properties that have elements, a measure of the variation energy having an atom when it is in state gaseous and when it has an electron to the layer of valence.

In other words, we can say that electronic affinity is the ability of a given atom to accept an electron, it is a type of energy that is produced when an electron is added to an atom when it is in a gaseous state. It is important to mention that those atoms that have a stronger nuclear charge will have a better electronic affinity.

  • Periodic properties of electron affinity
  • How it is determined
  • How it increases
  • How it differs from ionization energy
  • Importance
  • Elements with higher electron affinity
  • Other examples

Periodic properties of electron affinity

It has several periodic properties, including the following:

  • Negative electronic affinity property that implies the detachment of energy and is present at the moment in which the atoms manage to acquire a configuration with greater stability when they capture an electron, for this reason, the attractive force is the one that predominates in this property.
  • Positive electronic affinity is based on the absorption of energy and is present when energy must be provided to the atom so that it has the ability to capture the ion.
  • Electron affinity has negative values.
  • It has the ability to increase to the right when it is in the same period of the Periodic Table, this is because when its atomic radius decreases, the electron that is formed can be closer to the nucleus and for this reason, it can be attracted with greater force.
  • It can also increase upwards when it is in the same group or column of the Periodic Table because thanks to the smaller radius of the atom, the new electron can be attracted with greater force.
  • It can vary if it is in the same sense as ionization energy and electronegativity and when it is in the opposite part of the atomic radius.

How electron affinity is determined?

There are several cases in which it can be determined directly through the use of electron beams that collide with atoms when they are in the gas phase. A process called extrapolation can also be used, although this is a less precise way. Various representative scales are used to determine electronic affinity as it is a rather complicated process.

How it increases

The electronic affinity of the elements can increase ascending by groups and it does it from left to right in the periodic table of the elements. The affinity can also increase when the size of the atom decreases, it can also increase from the bottom up, in the same way, that electronegativity does.

How does Electron Affinity differ from ionization energy?

The main difference that exists between them is that ionization energy is that type of energy that is necessary to be able to start an electron from an element that is in a gaseous state, this can be represented as follows:

X ° (g) + I ⇒ ⁺ + e 

On the other hand, electronic affinity is a type of energy that can be extracted or supplied in order to transform a neutral atom into a negative ion, when it is in a gaseous state, it is a property that can measure the tendency of an atom and is represented as follows:

X ° (g) + e ⁻⇒ ⁻ + A


This type of chemical property is important because thanks to it it is possible to predict the oxidizing character of an element in the Periodic Table because it can act as an oxidant by having the ability to accept electrons.

Elements with higher electron affinity

The elements that have a better electronic affinity are those that are located on the right-hand side of the Periodic Table, specifically in block p, and they are elements that can also manifest their non-metallic character. The highest affinities are found in the elements that belong to group 17 and later, those that are located in group 16.

Other examples

Some examples are mentioned below:

  • Electron affinity for hydrogen: 72.8 kJ / mol.
  • The electronic affinity of oxygen: 141 kJ / mol
  • Electron Affinity for Fluorine: 328 kJ / mol
  • Silicon electron affinity: 133.6 kJ / mol
  • Electronic affinity for iodine: 295.2 kJ / mol
  • Lithium electronic affinity: 295.2 kJ / mol
  • Nitrogen electron affinity: 7 kJ / mol
  • Carbon electron affinity: 153.9 kJ / mol

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