What is chemical impenetrability?

The chemical impenetrability is a property that has the stuff that does not allow two bodies to be in the same place and the same time simultaneously. It can also be seen as the characteristic of a body that, along with another quality called extension, is accurate in describing matter.

It is very easy to imagine this definition at the macroscopic level, where an object visibly occupies only one region in space and it is physically impossible for two or more objects to be in the same place at the same time. But at the molecular level, something very different can happen.

Chemical impenetrability
According to the property of chemical impenetrability, matter can only be in one place in the same time and space

In this area, two or more particles can inhabit the same space at a given moment or a particle can be found “in two places” at the same time. This behavior at the microscopic level is described through the tools provided by quantum mechanics.

In this discipline, different concepts are added and applied to analyze the interactions between two or more particles, establish intrinsic properties of matter (such as energy or the forces involved in a given process), among other extremely useful tools.

What is chemical impenetrability?

In quantum mechanics, two particles can be in the same place at the same time

Chemical impenetrability can be defined as the ability of a body to resist its space being occupied by another. In other words, it is the resistance that matter has to be crossed.

However, in order to be considered as impenetrability they must be bodies of ordinary matter. In this sense, bodies can be traversed by particles such as neutrinos (classified as non-ordinary matter) without affecting their impenetrability, since no interaction with matter is observed.

Properties of chemical impenetrability

When speaking of the properties of chemical impenetrability, one must speak of the nature of matter.

It can be said that if a body cannot exist in the same temporal and spatial dimensions as another, this body cannot be penetrated or pierced by the one mentioned above.

To speak of chemical impenetrability is to speak of size, since this means that the nuclei of atoms that have different dimensions show that there are two classes of elements:

  • Metals (they have large cores).
  • Nonmetals (they have small size cores).

This is also related to the ability of these elements to be traversed. 

So, two or more bodies endowed with matter cannot occupy the same area at the same instant, because the electron clouds that make up the present atoms and molecules cannot occupy the same space at the same time.

This effect is generated for the pairs of electrons subjected to Van der Waals interactions (force through which molecules are stabilized).


The main cause of the impenetrability observable at the macroscopic level comes from the existence of the existing impenetrability at the microscopic level, and this happens the other way around as well. In this way, it is said that this chemical property is inherent to the state of the system under study.

For this reason, the Pauli Exclusion Principle is used, which supports the fact that particles such as fermions must be located at different levels to provide a structure with the minimum possible energy, which implies that it has the maximum possible stability.

Thus, when certain fractions of matter come close to each other, these particles also do so, but there is a repulsive effect generated by the electron clouds that each one has in its configuration and makes them impenetrable to each other.

However, this impenetrability is relative to the conditions of the matter, since if these are altered (for example, being subjected to very high pressures or temperatures) this property can also change, transforming a body to make it more susceptible to being traversed by other.

Examples of chemical impenetrability


One can count as an example of chemical impenetrability the case of particles whose spin quantum number (or spin, s) is represented by a fraction, which are called fermions.

These subatomic particles exhibit impenetrability because two or more exactly the same fermions cannot be placed in the same quantum state at the same time.

The phenomenon described above is explained more clearly for the most well-known particles of this type: the electrons in an atom. According to the Pauli Exclusion Principle, two electrons in a polyelectronic atom are unable to have the same values ​​for the four quantum numbers ( n , l , m and s ).

This is explained as follows:

Assuming that there are two electrons occupying the same orbital, and the case is presented that these have equal values ​​for the first three quantum numbers ( n , l and m ), then the fourth and last quantum number ( s ) must be different in both electrons.

That is, one electron must have a spin value equal to ½ and that of the other electron must be -½, because it implies that both spin quantum numbers are parallel and in the opposite direction.

Through ordinary matter

A simple example of impenetrability at the macroscopic level is the inability of a person to pass with his body a concrete wall, a closed door or another body of ordinary matter.

Related Articles

Leave a Reply

Your email address will not be published. Required fields are marked *

Back to top button